Explanation
The correct option to fill in the blank is:
C) fewer
Explanation: The phrase "Not... than" indicates a comparison of quantity. When comparing quantities of countable nouns, we use "fewer" to indicate a smaller number. Option A) less is incorrect because "less" is used for uncountable nouns or quantities that cannot be counted. Option B) lesser is incorrect because it is not the appropriate form to compare quantities of countable nouns. Option D) few is incorrect because it functions as an adjective, while in this context, we need a comparative form. Therefore, "fewer" is the correct option.
