One reason I can think of is that in choice B, "weighing less that 11 ounces" appears to be an attribute of the handheld computer and not the camcorder.

Other comments welcome.

First of all, PLEASE don't post the answer. You could have taken the snapshot, without selecting the correct answer.

IMO D ->

A/E - "....length of which is that of...." is an awkward construction.
Also, in A "..., and it weighs..." antecedent of "it" is not clear. "It" is refering to camcorder or computer..

In B/C, "...world, which...." Here "which" is refering to the world instead of refering to camcorder


In D, "...digital camcorder, which...." is correct construction and D has no pronoun reference error