conjunction usage?

[sachin.w]

Compared to alligators, crocodiles are better able to tolerate high salinity, because, unlike alligators, the glands on crocodiles' tongues can expel salt.


Compared to alligators, crocodiles are better able to tolerate high salinity, because, unlike alligators, the glands on crocodiles' tongues can expel salt

Unlike alligators' tongues, salt can be expelled through the glands on crocodiles' tongues, making crocodiles better than alligators at tolerating high salinity

Salt can be expelled through the glands on crocodiles' tongues and not through those on alligators' tongues; therefore, compared to alligators, crocodiles are more tolerant of high salinity

Unlike alligators, crocodiles can expel salt through the glands on their tongues; crocodiles are thus more tolerant of high salinity than are alligators

Compared with alligators, crocodiles are better at tolerating high salinity, because they can expel salt through the glands on their tongues while alligators' tongues cannot



The presence of and in bold above is one the reasons why ans is wrong.
My Question is does gmat test on the basis of conjunction usage?

[tim]

i can think of a better word to use, but i can't say for certain that the presence of "and" is definitively wrong. keep in mind though that ALL words in SC are fair game for the GMAT to test you on, although i can't recall seeing this particular thing being the deciding factor in a question..