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OG 15 SC.

hope nn can explain it?THANKS.

15.   In his research paper, Dr. Frosh, medical director of the Payne Whitney Clinic, distinguishes mood swings, which may be violent without their being grounded in mental disease, from genuine manic-depressive psychosis.

(A) mood swings, which may be violent without their being grounded in mental disease, from genuine manic-depressive psychosis

(B) mood swings, perhaps violent without being grounded in mental disease, and genuine manic-depressive psychosis,

(C) between mood swings, which may be violent without being grounded in mental disease, and genuine manic-depressive psychosis

(D) between mood swings, perhaps violent without being grounded in mental disease, from genuine manic-depressive psychosis（C）

(E) genuine manic-depressive psychosis and mood swings, which may be violent without being grounded in mental disease

The best choice is C because it uses the idiomatically correct expression distinguishes between x and y and because it provides a structure in which the relative clause beginning which may be violent clearly modifies mood swings. The other choices use distinguishes in unidiomatic constructions. Additionally, their in A is intrusive and unnecessary, and the modifier of mood swings in B and D (perhaps violent) is awkward and less clear than the more developed clause which may be violent

in fact that " distinguish "can be used as distinguish .sth ...from sth....,and one  part before and is a sentence while the other part is a phrase in the  the answer (C) ,is there a little unparallel in the answer C?why not choose (b)?

between x and y

between mood swings...,and genuine manic-depressive psychosis

答案一目了然阿

why not A?" distinguish "can be used as distinguish .sth ...from sth....,