Which of the following sentences has a compound predicate?

a. she washed the shells and dried them in the sun.
b. she placed the shells in a plastic bag while he dried himself off.
c. while he swam, she collected shells.
d. she raced along the path to beat him to the beach.

A. She washed the shells and dried them in the sun.

 The sentence is “She washed the shells and dried them in the sun”. A compound predicate actually consists of two or more than two verbs having the same subject and joined by any conjunction like “or” or “and”. As far as the given sentence is concerned, we see that “She” is the subject and the subject is doing two different things.  This is the reason behind taking this sentence as a compound predicate.