One more from GMATTER, please help

[chatekar]

A substance derived from the Madagascar periwinkle, which has proved useful in decreasing mortality among young leukemia patients, is cultivated in China as part of a program to integrate traditional herbal medicine into a contemporary system of health care.

A. A substance derived from the Madagascar periwinkle, which has proved useful in decreasing mortality among young leukemia patients,

B. A derivative, which has proved useful in decreasing mortality among young leukemia patients, of the Madagascar periwinkle,

C. A Madagascar periwinkle derivative, which has proved useful in decreasing mortality among young leukemia patients,

D. The Madagascar periwinkle has a derivative which has proved useful in decreasing mortality among young leukemia patients, that

E. The Madagascar periwinkle, a derivative of which has proved useful in decreasing mortality among young leukemia patients,

The OA is E, my answer was D.
There doesn’t seem to be much difference between the two except the organization of the sentence. Can anyone please advice on why D is wrong.

[givemeanid]

In D, 'that' seems to be referring to the entire phrase that precedes it and not just the periwinkle.
Also, 'is' following the comma should be referring to the periwinkle. The sentence reads "The Madagascar perwinkle is cultivated in China..." when you remove the phrase delimited by commas in E. That is correct.

[veekay]

A substance derived from the Madagascar periwinkle, which has proved useful in decreasing mortality among young leukemia patients, is cultivated in China as part of a program to integrate traditional herbal medicine into a contemporary system of health care.

A. A substance derived from the Madagascar periwinkle, which has proved useful in decreasing mortality among young leukemia patients,

B. A derivative, which has proved useful in decreasing mortality among young leukemia patients, of the Madagascar periwinkle,

C. A Madagascar periwinkle derivative, which has proved useful in decreasing mortality among young leukemia patients,

D. The Madagascar periwinkle has a derivative which has proved useful in decreasing mortality among young leukemia patients, that

E. The Madagascar periwinkle, a derivative of which has proved useful in decreasing mortality among young leukemia patients,

The OA is E, my answer was D.
There doesn’t seem to be much difference between the two except the organization of the sentence. Can anyone please advice on why D is wrong.

In all the options, except E, it is implied that the substance (derived from Madagascar) periwinkle is cultivate in China; however, Madagascar periwinkle is cultivate in China

[BTGmoderatorRO]

Option A.
The 'derivative' would have been a better explanation here to express that 'the Madagascar Periwinkle' has a substance extracted from it.
This option is wrong there are better options below.

Option B.
This option would have been correct but the 'derivative' and the Madagascar Periwinkle are placed too far apart and do not express unionism between the two.

Option c.
'The' would have been better used to express the proper noun 'Madagascar Periwinkle'
Thus this option is not correct.

Option D.
This is the correct answer.
This option established that the Madagascar Periwinkle has a derivative, to decrease mortality in young Leukemia patients.

Option E.
The Madagascar Periwinkle is not the derivative. But the only the leaf
Thus, this option is not correct.