Unlike transplants between identical twins, whose genetic endowment is

1. We can't eliminate based on the first word alone, but we can eliminate all the answers but C on the basis of faulty comparison. Each starts with a word that compares NOUNS, so in these choices, we are comparing the noun that follows (transplant(s)) with the subject of the sentence (all patients). The only way to make a correct answer starting with one of these words would be to compare "all patients receiving hearts . . " with some other group of patients: "Unlike patients with artificial hearts, all patients who receive heart transplants must .. . . " However, there's no way to do that in the context of this sentence, since it's illogical to say that ALL members of a group are unlike some members. ("Unlike my parents, ALL parents are strict." Huh???)

2. You're absolutely right when it comes to C. This ends up coming down to comma usage. When we see who/whose without a comma, it's typically a restrictive modifier--one that narrows down the scope of the previous noun. However, when we precede WHO/WHOSE with a comma, w are creating a nonrestrictive modifier. So A and E are saying that this is true of all identical twins.
_________________