Select the most appropriate option to fill in blank no. 2.
Show answer & explanation
Correct answer: D
Explanation
The correct answer is option 4 i.e. the.
Context: The blank refers to a specific “happiness chemical” already known or previously mentioned, so the definite article “the” is needed before it.
Meaning of the options:
One: refers to the number or a single unit; not suitable before a chemical name here.
An: indefinite article used before words starting with a vowel sound; does not specify a known or particular chemical.
A: indefinite article used before words starting with a consonant sound; also does not specify a particular chemical.
The: definite article used to refer to something specific or known.
Correct word: The
Reason: Since the passage talks about a particular “happiness chemical” that is enhanced, “the” is the correct article to use here. “One,” “an,” and “a” do not fit the context of specifying a known chemical.
Final sentence: It enhances the happiness chemical.
Hence, the chosen option will be correct.