Select the most appropriate option that can substitute the highlighted segment in the given sentence.
The young boy displayed an aptitude on scientific research.

Correct option is A

The correct substitution of the highlighted words is (a) aptitude for.

Explanation:
The word "aptitude" is always followed by the preposition "for" when it shows a natural ability or talent toward a field or skill.

• Incorrect: Aptitude on scientific research
• Correct: Aptitude for scientific research

Grammatical Rule Used:
Prepositions following certain nouns are collocations — fixed word combinations. “Aptitude” always takes “for” + [noun/gerund].

Example:
She has a strong aptitude for mathematics.

Information Booster:
Never say "aptitude on" or "aptitude at" unless followed by a specific activity (e.g., "aptitude at chess" is uncommon but can be found in literature; "for" is the standard for fields or disciplines).