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

Option “A” is the correct example of a sentence that has a
compound predicate. 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.