Demonstrate control of tenses and sentence structure.Our car broke down, so we came last.

Explanation

When two independent clauses are joined by a coordinating conjunction, the sentence is called compound sentence.Independent Clauses:"Our car broke down" is an independent clause because it forms a complete thought."We came last" is another independent clause because it also forms a complete thought.The comma is used to connect the two independent clauses. However, "so" is a coordinating conjunction .