Question

will medal and fan
Which is a compound-complex sentence?
A)
The dog began to bark at the visitor, and the cat ran under the chair.
B)
The teacher had just started the math lesson when the fire alarm bell began to ring.
C)
After they cleaned their rooms, the boys planned to go swimming, but it started to rain.
D)
Both the boys and the girls were excited about going to the mountains and spending the night.