Fill in the blank with the most appropriate word.

More than half the drain ______ been desilted.

has

More than half the drain has been desilted.

Explanation:

• Has: This is the correct verb form to use. "More than half the drain" is treated as a singular entity, so the verb should be in the singular form "has" to agree with it.

• Was: This verb form is not suitable in this context because it's past tense and doesn't match the structure of the sentence.

• Have: This verb form is not suitable here because "more than half the drain" is singular, so the verb should also be singular ("has").

• Is: This verb form is not suitable here because it's present tense and doesn't match the context of the sentence which indicates an action (desilting) that has already taken place.