My mother speaks in so a low voice that it is difficult to understand what she is saying.

Options

A. that it is difficult to understand
B. what she is saying.
C. My mother speaks
D. in so a low voice

Answer

D

Explanation

So. is placed before a modifier, an adjective or an adverb, to intensify its quality or manner. So + Adjective/Adverb + that + clause.. Eg: The meteor storm was so beautiful (adjective) that we watched it all night. However, *Such is placed before a modifier and noun to intensify the quality of the modifier. This clause can stand alone as a sentence or it can be paired with that + a clause to express an effect. Such + Adjective + Noun + that + a clause.. Eg: It was such a beautiful (adverb) meteor storm that we watched it all night. Similarly for the given sentence, .in such a low voice will be answer.