Select the most appropriate option to substitute the highlighted segment in the given sentence. If there is no need to substitute it, select ‘No improvement’.
Books costing money and requiring the user to read them for the idea to spread.

Correct option is A

The correct substitution of the highlighted words is (a) cost money and require.
Explanation:
The given sentence is not complete (it lacks a finite verb).
“Books costing money and requiring the user...” is a fragment, not a full sentence.
To make it grammatically correct, we need finite verbs — "cost" and "require".
Thus, the sentence should be: "Books cost money and require the user to read them for the idea to spread."
Grammatical rule used:
Use of finite verbs in independent clauses.
A sentence must have at least one subject and one finite verb to be complete.
Example:
Incorrect: Books costing money and requiring the user...
Correct: Books cost money and require the user...
Booster Tip:
Non-finite verbs like costing and requiring cannot function as main verbs unless they are part of a clause introduced with proper auxiliaries.