Once the company got onto the internet, the Dale and Thomas Popcorn Company quadrupled its business.
This is a complex sentence. It contains a dependent clause "Once the company got onto the internet" and an independent clause "the Dale and Thomas Popcorn Company quadrupled its business." Clauses contain a subject and a verb. Option B does not have two clauses because the first part "For two years" is a prepositional phrase. The first option is a simple sentence as well. The third option is a compound sentence because it has two independent clauses joined together with a comma and conjunction.
