Final answer:
A complex sentence can be formed by joining the two given sentences into one, with one clause functioning as an independent clause and the other as a dependent clause.
Step-by-step explanation:
To create a complex sentence from the two given sentences, we'll need to join them in such a way that one clause is independent (can stand alone) and the other becomes dependent (cannot stand alone). Here's a possible combination:
"As an unexpected thunderstorm began, my science class continued on its way to the abandoned gold mine." In this sentence, the clause beginning with "as" is the dependent clause, providing a condition for the independent clause, which is about the science class's continuation of its journey.