We play under that tree during childhood. A.

used to
B.

need to
C.

should
D.

will

used to

Explanation:

Im under the assumption that during childhood is in the past tense, so used to makes more sense

A. used to

Explanation:

The sentence states "during childhood", confirming that the speaker is referring to a memory from the past. Therefore we need an answer that represents the past.

Leaving us with A. Used To

answer: my favorite subject is choir

explanation: it is choir becuase you can sing and have fun singing at the same time with your friends.