Official Explanation
The argument is quite technical; try to focus on the big picture as much as possible. Here’s one possible way to map the argument on your scrap paper:
DSSC: cost less to make
efficient: TD nano
@ DSSC more success than other current SCs
The author cites two reasons why DSSCs are creating significant interest: they are less expensive to produce, and the use of a particular type of nanoparticle will help make DSSCs very efficient. The author concludes that these two advantages will make DSSCs more successful than any other competing products currently on the market; what must the author assume to draw this conclusion?
At the least, she is assuming that the other competing products can’t take advantage of these same benefits to reduce costs and improve efficiency. If it were the case that the competitors could use these benefits, too, then she wouldn't reasonably be able to conclude that DSSCs will be more successful than these other products.
To weaken the author’s conclusion, find a new piece of information that, if true, would make her conclusion at least a little less likely to be true.
(A) This is a trap assumption answer. The argument does indicate that efficiency is an important factor, but it does not claim that efficiency is the most important factor. The author is not assuming this to be true. Nor, if this were true, would it weaken the argument.
(B) Unrelated. The author is arguing about the success of the DSSCs relative to other solar cells. She is not discussing finding new uses for solar cells in general. In addition, her conclusion is specifically limited to a discussion of solar cells on the market today, not future technology.
(C) This is both a trap assumption and a trap weaken answer. The argument does mention the field of renewable energy resources but does not make any claims about other types of renewable energy; it discusses only solar cells. The conclusion specifically compares DSSCs only to other types of solar cells. Other sources, such as windmills, are therefore out of the scope of this argument. (Also: If it were true that other sources would not be as successful as solar cells, then the author’s argument would, if anything, be strengthened, not weakened.)
(D) This is both a trap assumption and a trap weaken answer. The argument claims only that the titanium dioxide nanoparticles are more efficient than anything investigated to date; it does not discuss what future research could uncover. (Also: If it were true that future research would not uncover more efficient nanoparticles, then the author’s argument would, if anything, be strengthened, not weakened.)
(E) Assumption required. The author claims that DSSCs are taking advantage of two benefits and, as a result, will be more successful than all other current solar cell technologies. In order to make this claim, the author must believe that the other solar cell technologies cannot themselves, for some reason, take advantage of both of these benefits to be successful.
(F) Possible fact to weaken. The argument provides two benefits for DSSCs (lower cost to produce, more efficient), but there could be other factors that serve to weaken the technology’s potential. If it is true that DSSCs are much less robust and don’t last as long, then the two benefits cited might not be enough to overcome these other weaknesses and allow DSSCs to be more successful than everything else on the market.