The correct answer is A. Idiosyncrasies are when someone has peculiar mannerisms and habits.
Step-by-step explanation:
In writing awkward or illogical constructions occur if there are issues on the different parts that are part of a sentence and the connection between those parts. In the case of the sentence, " Idiosyncrasies are where a person has peculiar mannerisms and habits" the word "where" seems to be inappropriate for this context as "where" refers to a place and in this case the author aims at defining the concept of idiosyncrasy. Because fo this, for improving this strange construction it is necessary to omit the word "where" and reorganize the sentence to define the word "Idiosyncrasies".
Considering this, the revision that does not improve the construction is " Idiosyncrasies are when someone has peculiar mannerisms and habits" because even though the word "where" has been omitted, changing it by the word "when" that refers to time does not clarify what idiosyncrasies are, also, it creates a confusing meaning as this sentence suggest idiosyncracies are not habits or mannerism but something that occurs which is not correct.