What is inserted before the direct object of a sentence if person?

If the direct object of a sentence is a person, you would typically insert a preposition before it, most commonly "to" or "for".

Examples:

* I gave the book to John. (Direct object = John, preposition = to)

* She wrote a letter for her grandmother. (Direct object = grandmother, preposition = for)

However, there are also instances where no preposition is used:

* I helped my neighbor. (Direct object = neighbor, no preposition)

The choice of preposition (or absence of one) depends on the specific verb and the intended meaning.

Here are some common verbs that take "to" or "for" before a person as a direct object:

* Give: I gave the book to John.

* Tell: I told the story to my friend.

* Show: I showed the pictures to my parents.

* Send: I sent a letter to my sister.

* Buy: I bought a present for my brother.

* Make: I made a cake for my mom.

Remember, the best way to determine the correct preposition (or lack thereof) is to consider the context and the intended meaning of the sentence.