Question

Yesterday's exam was _____ than the one last month.
a. difficult
b. difficulter
c. the difficultest
d. Yesterday's exam was _____ than the one last month.

Answer 1

es la respuesta "b"
bss

Answer 2

Creo que ninguna de las 3 son correctas.
Yo usaria more difficult

Porque:
Difficult es dificil 
Difficulter no existe
The Difficultest es el mas dificil de todos

Entonces la conclusion es q yo no creo q ninguna de esas tres sean utiles, yo usaria more difficult.

ESPERO QUE TE SIRVA