Answer:
Complex sentence.
Step-by-step explanation:
A complex sentence is the type of sentence that contains an independent clause as well as a dependent clause. This type of sentence is also joined by a subordinating conjunction, which comes either in between the dependent and independent clauses or it comes at the start of the sentence.
In the given sentence, the subordinating conjunction "if" comes at the start of the sentence. Moreover, the sentence contains one dependent clause "If it takes as long to explore the moon as it did to explore this continent" as well as one independent clause "our generation will not live to see the job finished."
Therefore, the given sentence is a complex sentence.