Answer:
B. We drove to the airport and picked up my cousins, who flew in from Toronto.
Explanation:
A complex sentence is composed of at least two clauses. An independent clause that can make sense on its own; and one or more of a dependent clause, which cannot make sense on its own and needs the independent clause to complete its meaning. Among the options shown in the question above, we can say that the complex phrase is "We drove to the airport and picked up my cousins, who flew in from Toronto." In this sentence the independent clause is "We drove to the airport and picked up my cousins", while the dependent clause is "who flew in from Toronto".
