While the thorns of all roses are protective, dissuading predators from feeding on the flowers’ blooms, unlike roses that grow in temperate climates, though, the thorns of desert roses also serve as reservoirs for water to forestall the ever-present threat of dehydration.
A- While the thorns of all roses are protective, dissuading predators from feeding on the flowers’ blooms, unlike roses
B- All roses’ protective thorns dissuade predators from feeding on their blooms; unlike those
C- The thorns of all roses are protective, dissuading predators from feeding on the flowers’ blooms; unlike those of roses
D- While all roses’ thorns are protective, they dissuade predators from feeding on the flowers’ blooms; unlike those of roses
E- The thorns of all roses are protective and dissuade predators feeding on their blooms, however, unlike those
Most important thing to note here is the presence of semi-colon. It is a very important punctuation and help us to cross out few answer choices. Option A is screwed up. It has incorrect modifier. Comma -splice issue. In short whenever you are forced to make sense out of an option eliminate it. A is gone.
B changes the meaning. Do roses have different type of thorns-protective and some others ? That's not correct , at-least in the light of the meaning of this sentence. Gone.
C -> looks ok. proper Independent clauses between sentence and closely related in meaning. Answer.
D. While blah blah... ; The sentence around semi-colon must be clauses and not dependent clauses. This is a common incorrect answer choice in sentences with semi-colon, in which option tries to connect Sub-ordinate clauses with semi-colon(Although the part after while is not a clause). That's an incorrect option choice. Co-ordinating conjunctions(FANBOYS) are used to connect Subordinate clause to an independent clause.
E. As a general rule in SC. Co-ordinating conjunctions take comma and other conjunctions take semi-colon. Note particularly however uses a semi-colon before it and a comma after it. Hence it is out.