Superheroes are fictional characters with 1) ________ powers who use their powers to fight crime and protect the public. Some popular superheroes include Superman, Batman, Spider-Man and Wonder Woman. Superheroes often have backstories that 2) ________ how they have gained their powers, 3) ________ being born with special powers, being bitten by a radioactive spider or being exposed to cosmic radiation. They usually have a specific outfit or clothing that they wear to hide their identity and protect 4) ________ while fighting crime. Superheroes have been a staple of popular culture 5) ________ decades, appearing in comics, movies, television shows, and video games.

Select the most appropriate option to fill in blank no. 2.

The correct answer is explain.

Step-by-step explanation:

1. Analyze the context: In the given passage, the sentence reads: "Superheroes often have backstories that 2) ________ how they have gained their powers..."

2. Identify Subject-Verb Agreement: The relative pronoun "that" acts as the subject of the relative clause and refers to the plural antecedent noun "backstories". Therefore, the verb following "that" must agree in number with the plural noun "backstories" and maintain the simple present tense used throughout the passage.

3. Evaluate the Options:
• explaining: This is a present participle and cannot serve as a finite verb without a supporting auxiliary verb.
• was explain: This is grammatically incorrect; the singular past tense verb "was" cannot be directly paired with the base verb "explain".
• explain: This is the base form of the verb, which functions correctly as a plural present tense verb agreeing with "backstories".
• had explain: This is grammatically incorrect; the past perfect auxiliary "had" must be followed by the past participle form ("had explained").

Therefore, explain is the most appropriate option for blank number 2.