My brother will come . . . . . . . . March. A. on B. to C. in D. out

The correct answer is C. in.

The preposition “in” is used to indicate a period of time, such as a month or a year. In this case, the speaker is saying that their brother will come during the month of March.

The other options are incorrect because they do not indicate a period of time. The preposition “on” is used to indicate a specific date, such as “on March 1st.” The preposition “to” is used to indicate a destination, such as “to March.” The preposition “out” is used to indicate a direction, such as “out of March.”

Here are some examples of how the preposition “in” is used to indicate a period of time:

• I will be in Japan in February.
• The meeting is in two weeks.
• The concert is in three days.
• The game is in an hour.

I hope this helps!