While the relative costs of concrete and steel are a predominant consideration in the design of a skyscraper, of no less importance to civil engineers is the time needed to fabricate the structural elements and the distance of the project site from the production sites of the raw materials.


A. of no less importance to civil engineers is the time needed to fabricate the structural elements

B. of no less importance to civil engineers are the time needed to fabricate the structural elements

C. of equal civil-engineering importance are the time in which the structural elements are fabricated

D. for a civil engineer, of no less importance are how long it takes to fabricate the structural elements

E. of equal importance to a civil engineer is the amount of time needed for fabricating the structural elements

This is a good example of how you have to concentrate on getting the best possible answer, even when all the five choices may seem to have something questionable about them. Here, none of the beginnings of the five options fits well with the opening of the fist clause: while the relative costs are ... . Clearly, however, one of them must be the best of the five, so forget about the beginnings and look at what else the options offer.

A quick scan shows that you have to choose between IS and ARE. In that case, what is the subject of these verbs? Within each option, there is a singular subject, so if you are rushing you may think that you should choose IS. Nevertheless, a careful reader will have noticed that after the underlined section there is an AND: and the distance. This means that the subject is plural and that you must therefore choose B, C, or D.

In B, you have the start of the sequence the time needed ... and the distance.
In C, the time in which ... and the distance.
In D, how long it takes ... and the distance
You can safely discard D: the sequence is definitely not parallel.

Between B and C, the sequence in B is more properly parallel than that in C. And if you are still in doubt, C offers you another basis on which to discard it: what exactly civil-engineering importance might be is a complete mystery.
The best answer is therefore B,