The last choice: la would be in the blank.
Espero que la temperatura no “ESTÉ” muy alta porque quiero hacer camping.
The correct word would be "Quien".
So, it would be "<span>¿</span>Quien compró los comestibles?"
Number 2! (Nosotros vemos las manzanas). The first one is conjugated to the 'yo' form, the third is conjugated to the 'el/ella' form, and the fourth is conjugated to the 'ellos/ellas/ustedes' form, which is wrong for the sentences.