Answer: Option C
The most appropriate preposition to fill the blank in the given sentence is "on". The correct sentence is "On the whole, I like the book very much." Let's understand why:
In the given sentence, "on the whole" is used to mean "considering everything; generally". It is an idiom and is always used with the preposition "on". Therefore, option C is the correct answer.
Here are some definitions of the idiom "on the whole":

• Taking everything into consideration; generally speaking (Cambridge Dictionary).
• All things considered; altogether (Merriam-Webster).

Additional Information:Prepositions are words that show the relationship between a noun or pronoun and other words in a sentence. Common prepositions include in, on, at, to, with, by, for, and of.
In this particular question, only one preposition is appropriate to use with the idiom "on the whole", and that is "on". The other options, such as "at", "from", and "in", are not appropriate in this context.
Therefore, the correct answer is option C, "on".