Answer:
A: Since the late 1970, many astronauts have held advanced degrees; this education has been useful for mission specialists.
Step-by-step explanation:
In the option A, the use of the semicolon in the is correct because it separates two statements that have related meanings. In this case, there are two independent clauses, and instead of using a conjunction, the writer prefered to use a semicoln to separate the two sentences. So, it functions the same as the conjuntion and.