Final answer:
A semicolon is needed to join two closely related independent clauses in the sentence. The correct implementation would be 'program; the,' separating the clauses about the selection of test pilots and the composition of the group.
Step-by-step explanation:
The sentence provided can be corrected by inserting a semicolon to join the two independent clauses. The appropriate place for the semicolon is between the clauses 'Seven test pilots were chosen for the first Mercury program' and 'the group consisted of Air Force officers.' Therefore, the part of the sentence that should be typed before and after the semicolon is 'program; the'.