Question

In the sentence "If your bicycle tire is low, use a pump to fill it with air.", which word is the direct object?

Answer 1

There are two direct objects in the sentence, pump and it.

Explanation:

The noun "pump" is the direct object of the verb "use".
The pronoun "it" is the direct object of the verb "fill".

Note: The adjective "low" is a type of object called a "predicate adjective", an adjective that follows a linking verb to restate the subject of that verb.
A linking verb is a verb that acts as an equal sign, its subject is or becomes the object (tire = low).