The correct option is
D especially
Answer : A
Explanation:
An adverb is a word that modifies / describes a verb, an adjective, another adverb or perhaps the whole sentence.
First, let's see what each of the words from the options mean:
--usually : generally
--Especially : particularly / specifically
--together : companionship / association
--only : solely
Tolstoy was a Russian writer (novelist), and the construction of the sentence suggests us that the speaker likes Russian novelists, but of them all he refers to one specific, i.e. Tolstoy.
Therefore the appropriate adjective for use from among the options is "especially".
Usually is grammatically inappropriate for use here because then it would not indicate speaker's preference towards a particular novelist (Tolstoy) and the sentence will not make sense.
Together cannot be used, because the other clause of the sentence focuses on a specific person. Thus it is grammatically inappropriate for use here.
Only means solely. And the sentence suggests that the speaker also likes other novelists and not just Tolstoy.
Therefore the correct complete sentence is:
I like all Russian novelists, ESPECIALLY Tolstoy.
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