The correct answer to the given sentence is "will return." Here's a detailed explanation:
Subject-Verb Agreement:
In the given sentence, the subject is "They," which is the third-person plural pronoun. When using third-person plural pronouns as the subject, we use the base form of the verb (return) with the auxiliary verb "will" to form the future tense.
Usage of "will":
The auxiliary verb "will" is used to express a future action or event. It is commonly used to talk about actions that are planned or that will happen in the future. In this case, "will" is used to indicate that the action of returning will happen in the future.
Forming the sentence:
To form the complete sentence, we combine the subject "They" with the auxiliary verb "will" and the base form of the verb "return." This results in the sentence "They will return."
Summary:
To summarize, the sentence "They ---- (return) as soon as possible" can be completed with the phrase "will return." This construction follows the subject-verb agreement and uses the auxiliary verb "will" to indicate a future action.