The people known as Sumerians are credited as starting the first civilization and building the first settlements worthy of being called cities.


(A) as starting the first civilization and

(B) with starting the first civilization and also

(C) for starting the first civilization and

(D) as the ones who started the first civilization and

(E) with starting the first civilization and

If you don't know whether the correct idiom is credited as, credited with, or credited for, you could approach this question from the point of view of parallel structure. The underlined section ends with AND; this means that starting in that section must be parallel with building in the other part of the sentence.
Since D uses started, you can eliminate it. But you still have four remaining.
B uses and also. This is considered a redundancy in the GMAT. Eliminate this option.
Nevertheless, you still have three remaining, A, C, and E, and each of them has the required form starting ... and building.

At this point, you have no choice but to rely on your knowledge of idioms. Since credited with is the correct idiom, option E is the right answer.