To help preserve ancient Egyptian monuments threatened by high water tables, a Swedish engineering firm has proposed installing pumps, perhaps solar powered,
to lower the underground water level and dig trenches around the bases of the stone walls.
Meaning: The high water tables are a threat to the Egyptian monuments. To resolve this issue a firm has proposed to do two things i) install pumps and ii) dig trenches. The reason why i) installing pumps was suggested is because by installing pumps the underground water level will reduce, thus reducing the water levels thereby reducing the threat.
(These pumps are probably solar powered)To help preserve ancient Egyptian monuments
(Stating a reason to a particular action)threatened by high water tables,
(Verb-ed modifier modifying "Egyptian monuments")a Swedish engineering firm has proposed
(Main Subject - Swedish engineering firm ; Main verb - has proposed)installing pumps, perhaps solar powered,
(additional information about the proposal) (element 1 of parallelism)to lower the underground water level
(additional information about the proposal to install pumps)and dig trenches
(second proposal made by the firm) (and - parallelism marker) (element 2 of parallelism)around the bases of the stone walls.
(additional information as to where the trenches must be dug) Quote:
(A) to lower the underground water level and dig trenches
As discussed above the firm proposed two things. 1) Installing pumps and 2) digging trenches. Now in the non-underlined part of the sentence we have "installing pumps". Thus to maintain parallelism the second element
dig trenches must be written in the same structure i.e.
digging trenchesHence, due to faulty parallelism (A) is incorrect
Quote:
(B) to lower the underground water level and to dig trenches
(B) By placing "to" before "dig trenches" we have made it parallel to "underground water". So now the sentence illogically states that installing pumps does two things 1) It lowers groundwater level and 2) it digs trenches
Due to illogical meaning conveyed, by faulty parallelism, (B) is incorrect
Quote:
(C) to lower the underground water level and digging trenches
As stated above "installing pumps" and "digging trenches" must be parallel.
Quote:
(D) that lower the underground water level and that trenches be dug
By placing a "that" before trenches it seems as if "trenches" is parallel to "lower groundwater". If this isn't convincing then notice the structure "trenches be dug". I believe this is a passive construction which is completely avoidable given choice (C)
Quote:
(E) that lower the underground water level and trench digging
Trench digging? We say "digging trenches" and not "trench digging" Why? I am not too sure? Probably an Expert
GMATNinja could comment on this one.
Correct:
(C)