For decades Surgeon Generals have warned that smoking

C it is. The choices given are trying to test parallelism in the sentence, obviously. A is out because of the redundant use of the conjunction "and". in choice B, "low birth weight risks" is awkward. Contrary to A, Choice D completely eliminates the well needed conjunction "and". Choice E compounds the error in D by throwing the parallelism out of the window using "complicating", in addition to the missing conjunction "and".
C is the best choice, because it uses the conjunction "and" at the right place and uses the comma appropriately.

OA is D,but I dont' feel convinced by OA

ngobaotrung - what is the source of this quesion? The OA does not make any sense to me. Could anyone explain why it is D, if it is indeed D?

I think D makes a lot of sense.

For decades Surgeon Generals have warned that smoking increases the risk of lung disease,including lung cancer and emphysema, and can complicate pregnancy,and increases the risk of low birth weight

A.
B.can complicate pregnancy,and increases low birth weight risks
C.and can complicate pregnancy,increasing the risks of low birth weight
D.can complicate pregnancy by increasing the risks of low birth weight
E.complicating pregnancy by increasing the risks of low birth weight

C and E have misplaced modifiers. C seems to indicate that pregnancy is increasing is the resk of low birth weight. E tries to parallel complicating with including...
A uses more ands than necessary and does not explain the meaning properly.
B is close but D clearly shows that I can complicate pregnancy by {reason for complicated pregnency) increasing the risks of low birth weight .

ngobaotrung plz check the answer ! D) cannot be right. the sentence makes no sense at all.

I got C but think that ritesh has a point. D may be correct.

D) only makes sense when a conjunction is added. ngobaotrung, did you copy the right answers ??? does anyone has kaplan 800 ?

Do you have the OE then?

I'm a bit confused about how the answer can be D...the sentence makes no sense without the word 'and' before 'can complicate'...had there been an 'and' i would have picked D but chose C instead because of this reason

cloudz9 & christoph

Try reading the sentence like this

For decades Surgeon Generals have warned that smoking
increases the risk of lung disease,including lung cancer and emphysema, and
can complicate pregnancy by increasing the risks of low birth weight.

Everything in Red indicates a subject
Everything in Green indicates verb

Whet else needs to be parallel??

Firstly, for the future reference (God knows who else will dig this out ) I have to mention that the answer choice D in original post was indeed incorrect:

D. and can complicate pregnancy by increasing the risks of low birth weight

Secondly, I still have a question on this one: why does Kaplan (or whoever) take as a fact the subordination between complicated pregnancy and low birth weight risks? Yes, they are indeed related, but to me the risks seem to be a possible consequence of complicated pregnancy, not the reason. Eh? What's wrong with B?

I checked KAPLAN GMAT800, and I found typo on D posted by ngobaotru.

For decades Surgeon Generals have warned that smoking increases the risk of lung disease,including lung cancer and emphysema, and can complicate pregnancy,and increases the risk of low birth weight.

A. and can complicate pregnancy,and increases the risk of low birth weight
B. can complicate pregnancy,and increases low birth weight risks
C. and can complicate pregnancy,increasing the risks of low birth weight
D. and can complicate pregnancy by increasing the risks of low birth weight
E. complicating pregnancy by increasing the risks of low birth weight

Definitely, the correct answer is D. No doubt about it.

After the correction, (D) makes perfect sense. This SC, as originally written, had me flummoxed

For the same reason, I chose B.
If D is the right answer(which lacks sense), what is wrong with B?