The woodland sub-species were in isolation from

The woodland sub-species were in isolation from contact with humans longer than either their marsh cousins or the tree-dwelling sub-species.  

A.  in isolation from contact with humans longer than
B.  isolated from contact with humans longer than
C.  in isolation from contact with humans longer than were
D.  isolated from contact with humans longer than were
E.  in isolation and without contacts with humans longer than

The best answer is D. The phrasing of the comparisons in choices A, B, and E is incomplete, so the comparisons are ambiguous.  Choice D employs concise, idiomatic phrasing to express a logically complete comparison.


Drinking milk enriched with vitamin D may significantly reduce the risk of rickets and also aid for sufferers of heart disease, according to studies recently completed at the University of California in San Francisco.  

A.  significantly reduce the risk of rickets and also aid for  
B.  be significant in reducing the risk of rickets and aid for  
C.  significantly reduce the risk of rickets and aid  
D.  cause a significant reduction in the risk of rickets and aid to  
E.  significantly reduce the risk of rickets as well as aiding  

The best answer is C.   Choices A, B and D each produce a clearly unintended meaning: by using aid as a noun rather than a verb, each creates a misleading parallel with the noun risk.  Choice E lacks grammatical parallelism.