Some scientists have been critical of the laboratory tests

[charmanineW924]

2. ' able to ' and ' able to be ' looks awkward in the sense that they have added more words when we have a precise 'can/could'

the problem is worse than that. it's actually WRONG to use 'able' here.

read:
https://www.manhattanprep.com/gmat/foru ... tml#p94106

let's ask ourselves: who is ABLE (or unable) to do something here?
the issue is that humans are able to consume only X amount of these substances (before they get cancer, presumably).
so it makes sense to say "humans are able...", but not "carcinogens are able...".

I just want to be more clear about this quetion. Do you mean that "are able to be aonsumed " in D is wrong? what about " are able to " in C?
I think it is Ok to use both "can" and "be able to" in choice C. Is it right?

[tim]

If something is able to be consumed by humans, that is very different from saying that humans are able to consume it. It all comes down to who or what has the "ability".

[RonPurewal]

It all comes down to who or what has the "ability".

this issue ^^ applies to the word 'able'/'ability', as well as to the word 'capable'/'capability'.

it does NOT apply to the word 'can', which can be used freely both ways.

e.g.,
Humans are unable to hear the cry of animal X. -- correct
Humans are incapable of hearing the cry of animal X. -- correct
Humans cannot hear the cry of animal X. -- correct

The cry of animal X is unable to be heard by humans. -- INCORRECT
The cry of animal X is incapable of being heard by humans. -- INCORRECT
The cry of animal X cannot be heard by humans. -- correct

the two sentences marked 'INCORRECT' are wrong because the (lack of) ability belongs to the human ear, not to the sound itself.
this is a non-issue with the word 'can'.
'can(not)' just means that something is (im)possible, without reference to the possessor of whatever ability might be necessary.

[JbhB682]

It all comes down to who or what has the "ability".

this issue ^^ applies to the word 'able'/'ability', as well as to the word 'capable'/'capability'.

it does NOT apply to the word 'can', which can be used freely both ways.

e.g.,
Humans are unable to hear the cry of animal X. -- correct
Humans are incapable of hearing the cry of animal X. -- correct
Humans cannot hear the cry of animal X. -- correct

The cry of animal X is unable to be heard by humans. -- INCORRECT
The cry of animal X is incapable of being heard by humans. -- INCORRECT
The cry of animal X cannot be heard by humans. -- correct

the two sentences marked 'INCORRECT' are wrong because the (lack of) ability belongs to the human ear, not to the sound itself.
this is a non-issue with the word 'can'.
'can(not)' just means that something is (im)possible, without reference to the possessor of whatever ability might be necessary.

Hi Ron - so it seems like what you are saying is "able to / unable to" and "capable of /incapable of" cannot ever be used in the passive voice construction because of the meaning issue

Furthermore, seems like "can" is an option to use in the passive voice

What other phrases like "Able to/unable to" or "Capable of / incapable of" , should never be used in the passive construction because of meaning issues ?

I think if there isn't any , test takers will just have to memorize these 2 exceptions only

[Sage Pearce-Higgins]

That seems like an unduly restrictive rule. How about this example: "He is incapable of being loved." That seems like a fair sentence, even though the meaning tends towards 'He is incapable of accepting love.'

In any case, I'd encourage you to hone your skill of looking at the meaning of each sentence and weighing it up, rather than trying to find really quite an obscure and specific rule which, realistically, you've got a very small chance of every applying again.

[JbhB682]

Hi Sage - Following up on Ron's examples, could you confirm if my understanding is accurate

(made up) -- : The oxygen able to be consumed by Humans is declining because of pollution = wrong

(made up) -- The oxygen consumed by Humans is declining because of pollution = accurate

[Sage Pearce-Higgins]

Hi, no need to quote my last post when you write. Here are my thoughts on your sentences:

The oxygen able to be consumed by Humans is declining because of pollution = wrong

I agree with you that this sentence is wrong. It suggests that the oxygen itself is able to do something.

The oxygen consumed by Humans is declining because of pollution = accurate

Sure, this sentence is fine. However, the meaning is different from the above sentence because it misses out the issue of possibility. There's a distinction between what humans actually consume and what they can consume. I might say 'The oxygen that humans can consume...', or 'Humans' ability to consume oxygen...' depending on which nuance of meaning is required.

[RAHULS852]

1: what is the difference between "far" and "by far", I understand that the use of "far" in choice A is to modify the verb "exceed", but how about the use of "by far" in choice B and D, it is right?

this is a non-issue.
'far exceed' is fine.
'exceed by far' is also fine.

2: why do we need "that" before "those" in choice B and C?

you don't.

Hi Sage/ Manhattan Expert,

I think Ron wanted to say that you don't need "that" before "those" but after "those".
Without "that" sentence will not make sense.

eg: 1) Kites are harder to find in my neighborhood, as the only shop sold them has closed
2) Kites are harder to find in my neighborhood, as the only shop that sold them has closed.

In Ist example without "that" 2 verbs are not making sense but in 2nd "sold" is part of modifier.

Kindly review my understanding.

Regards,
Rahul Singh

[Sage Pearce-Higgins]

To be clear, we need the word 'that' in the correct answer. If there was no 'that', then we might get mixed up and think that the sentence is referring to 'those humans', rather than 'those [amounts]'.

eg: 1) Kites are harder to find in my neighborhood, as the only shop sold them has closed
2) Kites are harder to find in my neighborhood, as the only shop that sold them has closed.
In Ist example without "that" 2 verbs are not making sense but in 2nd "sold" is part of modifier.

Nice examples. I agree that (2) has a really clear 'noun that' modifier. There are, however, more subtle examples. We tend to leave out the word 'that' in some sentences, for example, after certain verbs: e.g. 'He told me he loved me.' This is totally fine in ordinary English, but GMAT tends to clarify things with 'that': 'He told me that he loves me.'

[RAHULS852]

Thanks Sage.
You have cleared my doubt.

Regards,
Rahul Singh

[Sage Pearce-Higgins]

You're welcome.