Identify the type of sentence. if it takes as long to explore the moon as it did to explore this continent, our generation will not live to see the job finished.

 The sentence given would be a:    complex   sentence.
 
Explanation:

     →  {since the sentence given contains ONE independent clause and ONE dependent clause.}

The sentence given is:

   →  "If it takes as long to explore the moon as it did to explore this continent, our generation will not live to see the job finished."

In this sentence given, the only [one, single] independent clause is: 

    →  "...our generation will not live to see the job finished."

Note: An 'independent clause' refers to a group of words that could form a sentence on its owns—with a subject and a predicate; and can form a "complete thought" on its own.

The aforementioned 'independent clause' could be written to form a complete sentence and independent thought on its own, as: 

      → {"Our generation will not live to see the job finished."} .

Furthermore, in this sentence given in the original question:

 "If it takes as long to explore the moon as it did to explore this continent, our generation will not live to see the job finished." ;

   →    the ONLY  [one, single] dependent clause is:

"If it takes as long to explore the moon as it did to explore this continent...";

Note:  A 'dependent clause' does not form a full sentence or independent thought on its own (although a 'dependent clause' may contain both a subject and a verb) and often begins with a so-called 'dependent marker' (such as:  after, as, if, although, even though, when, while and other others).  

Note that the the original sentence given in the problem does begin with a 'dependent marker' — in this case, "If" . 

Since a 'dependent clause' cannot form a complete sentence (or complete thought) on its own, it must be followed by at least one 'independent clause'.  

By definition, the sentence given in this question is a  complex sentence  because there is only ONE dependent clause AND only ONE independent clause in the sentence. 

 Hope this answer — AND lengthy, accompanying explanation — provides some helpfulness and usefulness.

The answer would be d, coherence.