Answer:
<u>He</u> wants to earn a scholarship.
Explanation:
Singular refers to a single thing, person, instance, event or group, and pronoun refers to substitutes of nouns or noun phrases, such as I, you, we, they, he, she, it, me, us, them, him, among other.
So, sentence number 2 is the one that contains a singular pronoun because it has "He", which it's a third-person singular pronoun.
The other options are incorrect because "We" is plural (Option 1 and 4) and "They" and "us" are also plural pronouns (Option 3).