请教一个语法模拟题

The electronics company has unveiled what it claims to be the world's smallest network digital camcorder, the length of which is that of a handheld computer, and it weighs less than 11 ounces.

a. to be the world's smallest network digital camcorder, the length of which is that of   a handheld computer, and it weighs

b. to be the smallest network digital camcorder in the world, which is as long as a handheld computer, weighing

c, is the smallest network digital computer in the world, which is as long as a handheld computer, and it weighs

d. is the world's smallest network digital comcorder, which is as long as a handheld compiter and weighs

e. is the world's smallest network digital camcorder, the length of which is that of a handheld computer, weighing

答案是d, 我选a. 我知道a 的其中之一缺陷是it 指代不清，但相对d 在 has unveiled what it claims 后用is 是个小错呀。

如果根据答案d 按以下符号划分结构，各部分是做何成分呢？The electronics company has unveiled [(what it claims) is the world's smallest network digital comcorder ], which is as long as a handheld compiter and  weighs less than 11 ounces.

实在困惑d 的结构，请nn 指教，先谢了。

d. is the world's smallest network digital comcorder, which is as long as a handheld      compiter and weighs.

'is' in choice D is redundant.

答案d 应该不会错，因这是gmatprep软件里提供的，可能是我们对该句语法点还存在盲点，还有没有更多的nn 一起分析一下？

The electronics company has unveiled what (it claims) is the world's smallest network digital comcorder, which is as long as a handheld compiter and  weighs less than 11 ounces.

if we omit "it claims", the clause "what...." is object part of the whole sentence.  "which" refers to comcorder. "it claims" is a parenthesis component. D is just fine.