Answer:
the correct answer in both is "de la".
Step-by-step explanation:
el profesor esta delante de la clase = right
el profesor esta delante del clase = wrong
Cerca de la casa hay un patio = Right
Cerca del casa hay un patio = Wrong
del = de + el
you can say "una manzana cayó al lado DE EL árbol" or "una manzana cayó al lado DEL árbol"
Both are technically fine, but the one that is really fine would be "del" and your teacher may correct you if you write "de el".
del = de el = of
the words "de la" do not have a mixture like "de el"
del = de el. (male)
de la = de la (female)