A number fewer/less than

[RobinG157]

Since 1868, approximately thirty-five shipwrecks have been recorded off Alaska, a region known for their treacherous seas—less than those recorded off the coast of Massachusetts.

A. their treacherous seas—less than that

B. its treacherous seas, a number fewer than that

C. its treacherous seas, which is less than those

D. its treacherous seas—fewer than have been

E. their treacherous seas, fewer than the ones

I came across this question on gmatclub.com. The right answer to this question is D. I want to know whether the construction in option B "a number fewer than X" is correct. Which of the following is better in this kind of situation:

a. xxxxxxxxx, a number fewer than xxxxxx.
b. xxxxxxxxx, a number less than xxxxxx.

Thanks in advance.

[RonPurewal]

we need the original source of the problem (= whoever actually owns the copyright)—not another forum or other secondhand source.

[RonPurewal]

also, this problem is a rip-off of the following item from GMAT PREP:
https://www.manhattanprep.com/gmat/foru ... t4278.html
this problem adds no further value, so there's no point in considering it. (hopefully you didn't pay money for it!)

that thread already has over a hundred posts, so your question will almost certainly be answered somewhere in there.