Question

Which word in the sentence is a direct object? a grapefruit tree can produce 1,500 pounds of fruit each year?

Answer 1

grape fruit,,,,,,,,,,,,,,

Answer 2

Fruit... is the direct object

For example:
The girl kicked and screamed.
Nothing is being kicked or screamed here. Those are both intransitive verbs because no action is being transferred.

However,
The girl kicked the ball.
Here, if you ask, "what or who is being kicked," you would answer "the ball." Therefore the ball is the object.