Q10 - All bridges built from 1950

[rsmorale]

Please help me figure this out. I chose A. Why is C the credited response?

[maryadkins]

This is an inference question, so we'll take everything in the argument as true and infer based on that information. We know:

-ALL bridges built from 1950-1960 need rehab
-Some of these have faulty design
-None of the ones with faulty design are suspension bridges
-Some of the bridges that need rehab are not suspension bridges

We are looking for a statement that must be true based on these.

(A) is incorrect because we don't know anything about the suspension bridges that DO exist and what they need--we're just told that none of the faulty design bridges are suspension, and that some of the bridges are not suspension.
(B) is like (A)--it focuses on what we can conclude about suspension bridges. But again, all we're told about them is where they DON'T exist.
(C) is true based on the first two statements. If all bridges in the period need rehab, and if some of them are faulty, then some of them need rehab. All + Some (of the all) = Some
(D) is the opposite of what the argument tells us.
(E) is also the opposite of what the argument tells us. We know that none of the faulty design bridges are suspension bridges.

[mxl392]

Would it be wrong then to conclude that "some ARE B" if the stimulus said "some ARE NOT B"?

I mean, technically, it would be wrong, but it defies common sense for a person to say "Some of the fruits in the basket are not apples." It could be true that there are no apples, but you would only say that if there were apples in the basket... right?

[timmydoeslsat]

The entire some = possibility of all (aka not even a some are not) is due to this kind of scenario:

Imagine the Chicago Bulls team is having a meet and greet with fans. You go to this event. The first player you attempt to shake hands with actually kicks you in the shin. You move on to the next player: same thing, a swift kick to the shin. You move to the next player who then greets you with shin kick.

You have met 3 of the 12 Chicago Bulls' players. You leave the event after having your shin treated like a soccer ball.

Someone asks you how the event went. You tell them that some of the Chicago Bulls players are not nice.

What about the other nine guys you did not greet? They could have shaken your hand and bought you ice cream. Or they could have kicked you in the shin.

One thing you know for sure, some of the players are not nice. This is all that you know. It could be true that the some you stated actually means all. It could be true that the some you stated may in fact only be a minority of the players you greeted.