Answer: Option C, Escribe
Explanation: The sentence "El alumno ____________________ (cubrir/escribir) en el cuaderno."
means:
"the student__________ in the notebook"
The options to complete the blank are:
A: Escribes
B: Cubres
C: Escribe
D: Cubre
Both options A and B are in the wrong person, so we can discard them, now let's analie the options C and D.
C; escribe means "write" and D, cubre means "covers"
The option that makes more sense in the context of the sentence is "writes", then the full sentence would be:
"el alumno escribe en el cuaderno"