Sentence Correction

The type of behavior exhibited when an animal recognizes itself in a mirror comes within the domain of "theory of mind," thus is best studied as part of the field of animal cognition.

A.of "theory of mind," thus is best
B."theory of mind," and so is best to be
C.of a "theory of mind," thus it is best
D.of "theory of mind" and thus is best
E.of the "theory of mind," and so it is best to be

OA:D

NandishSS wrote:The type of behavior exhibited when an animal recognizes itself in a mirror comes within the domain of "theory of mind," thus is best studied as part of the field of animal cognition.

A.of "theory of mind," thus is best
B."theory of mind," and so is best to be
C.of a "theory of mind," thus it is best
D.of "theory of mind" and thus is best
E.of the "theory of mind," and so it is best to be

OA:D

A - "thus" is an adverb and cannot be used as a conjunction.

B - the basic structure in the second part is -
"the theory is best to be studied as part of ..." - Incorrect.

Removing "to be" makes the sentence clearer.

C - ",thus it is best studied ..." - this is a run-on sentence.

D - correct answer.

E - "to be" makes this incorrect.