Question

—¿qué hay en tu mochila? —pues, hay ______ en mi mochila.
una papalera y una bandera
un cuaderno y un lapiz
un escritorio u un boligrafo
una mesa y una silla

Explanation:

The question asks what is in a backpack. We need to select items that are logically carried in a backpack. "un cuaderno y un lápiz" (a notebook and a pencil) are typical school/portable items that fit in a backpack, while the other options contain large furniture or non-portable objects that do not belong in a backpack.

Answer:

un cuaderno y un lapiz