Question

Which sentence below is a complex sentence?
a.
Some students like to study in the morning. c.
When he handed in his homework he forgot to give the teacher the last page.
b.
I tried to speak Spanish and my friend tried to speak English.
d.
The cat lived in the backyard, but the dog, who knew he was superior, lived inside the house.


Please select the best answer from the choices provided

A
B
C
D

Answer 1

D or so I believe should be the complex one?

Answer 2

c.......................