Answer:
C
Step-by-step explanation:
The complex sentence in the given options is:
C. When spectators attended jousts, they often rooted for a favorite knight.
This is a complex sentence because it has a dependent clause, "When spectators attended jousts," and an independent clause, "they often rooted for a favorite knight." The dependent clause cannot stand alone as a complete sentence and requires the independent clause to make complete sense.
Option A is a compound sentence as it consists of two independent clauses joined by the coordinating conjunction "and."
Option B is a simple sentence as it consists of only one independent clause.
Option D is also a simple sentence as it consists of only one independent clause.