¿cual es la idea principal?
explorar una cueva es mucho trabajo.
no duermo lo suficiente por la noche.
hay que usar zapatos especiales para escalar una cueva.
es divertido tener un picnic en una cueva

The main idea is outdoor activities.

Explanation:

Outdoor activities in Spanish means actividades al aire libre like un picnic, a picnic, usar zapatos especiales which means wear special shoes.

B. ¿Por qué no acampamos en las montañas?

This option is the more logical. Since hay una brisa fresca y hace sol is a positive sentence, it is common that a question comes after this. Since it's sunny outside, it's a great time to camp in the mountains with family or friends. Therefore, we can write a complete sentence as follows:

Hay una brisa fresca y hace sol. ¿Por qué no acampamos en las montañas?

Explanation:

ok its ok me to we can be friends bro