Which of the following sentences is an example of a compound sentence? select all that apply.

a) the dog sat and wagged his tail.
b) ben picked up his sister from preschool, while his mother drove his brother to soccer practice.
c) amy put on her tennis shoes to go for a walk, but the phone rang before she could leave.
d) the polar bear splashed and rolled through the water to the delight of the zoo’s visitors.