Rashed12 wrote:
Once Dr. Benner and his colleagues combined real atoms, according to his designs, the artificial bases didn’t work as he had hoped.
A. Once Dr. Benner and his colleagues combined real atoms, according to his designs, the artificial bases didn’t work as he had hoped.
B. Once Dr. Benner and his colleagues combined real atoms, according to his designs, the artificial bases didn’t work as he hoped.
C. As Dr. Benner and his colleagues combined real atoms, according to his designs, the artificial bases didn’t work as he had hoped.
D.Once Dr. Benner and his colleagues combined real atoms, according to his designs, he had hoped and the artificial bases didn’t work.
E. When Dr. Benner and his colleagues combined real atoms at any time, according to his designs, he had hoped and the artificial bases didn’t work.
Meaning: the bases didn't work as he HAD hoped, once he and the others combined real atoms.
Rule: Past Perfect Tense or "had" is used to describe an event in the past before another event in the past.
Here, we need "had" as the correct tense, because the Dr. "hoped" before he "combined the atoms", and both of these happened sequentially in the past.
(B) missing "had".
(C) "as" in this context can be used to indicate that something happens during the time when something is taking place, or it can be used to say "because" or "since"; both cases distorts the intended meaning: the bases didn't work because they combined the atoms, we can't infer that, maybe it was something else; also, the bases didn't work while they combined the atoms, they didn't work after or "once" they combined the atoms.
(D) "combined real atoms…he had hoped and the artificial bases didn’t work" this is not parallel and unintended.
(E) "combined real atoms…he had hoped and the artificial bases didn’t work" this is not parallel and unintended; also, "when" is used to express at or during the time that, which in this is unintended;
Answer (A).