Many of these gene flaws - there are plenty of them,

[ShrutiK984]

Many of these gene flaws - there are plenty of them, with names like BCR-ABL - are relative newcomers to medical terminology, as are a majority of the new anti-tumor drugs, still in early testing, that are aimed at them.

a- medical terminology, as are a majority of the new anti-tumor drugs, still in early testing, that are aimed at them.
b- medical terminology like a majority of the new anti-tumor drugs that are still in early testing, and aimed at them.
c- medical terminology, as are a majority of the new anti-tumor drugs that are still in early testing, aimed at them.
d- medical terminology like a majority of the new anti-tumor drugs, still in early testing, that are aimed at them.
e- medical terminology, as are a majority of the new anti-tumor drugs, still in early testing, and aimed at them.

Please help me understand how answer A is correct? and why is d incorrect.

This is a Veritas question and I dont have access to post/ask in their forum so I am asking here.

[RonPurewal]

this isn't a very good sentence, because (a) it's much harder to understand than GMAC's sentences, and, even worse, (b) it doesn't make sense by itself.
(the sentence starts with '...these gene flaws'. this must, of course, be a reference to something mentioned earlier. since there's no 'earlier' text, this is clearly a problem.)

still, D is in fact incorrect.
the construction 'NOUN(s) like X' describes NOUN(s) that are like 'X'.

e.g.,
I have never been able to find another pen like the one I used to write in my childhood journal.

[RonPurewal]

This is a Veritas question and I dont have access to post/ask in their forum

wait—you purchased V's material, but you still aren't allowed to post on their forum? really?