Billy bought pencils and put them in his what?\nOptions:\n- classroom\n- kitchen sink\n- backpack\n- cabinet\n- store
Let's think step by step.
backpack
Pencils are usually used in a classroom.

A pencil is a personal belonging.

Students generally bring their backpacks to classrooms.

Students usually keep their personal belongings in the backpack.

.

The answer: backpack