Two things:

1. "Disappearance" of lifestyles - singular - Seems should be used.
2. Need an adverb to modify doomed - Inevitably should be used.

Only choices that use these are B and C

C is incorrect because "which" points to aborigines instead of lifestyles

IMO B

Hi dumb doofus,

OA is E

Your first reasoning is correct. Disappearance should go with seems



Acc to me, B is rejected on 2 grounds:

1. doomed is a redundant word (disappearance is a synonym)
2. B gives an impression that 2nd clause modifies aborigines whereas it actually modifies lifestyles. So we insert lifestyles


More comments welcome!!
Cheers!!
Turbo Jet

disappearance of lifestyles....seems inevitable.

B) What is the phrase "requiring vast..." modifying here? It looks like the phrase is modifying the previous clause, in which case, it would be modifying the "disappearance of lifestyles" -- Does not make sense.

C) Pretty obvious -- which should modify "aborigines" here;however, this is not the intent, so C is out.

D) This looks good except for the seem, when we need seems. The "That" clause actually is much better than the -ing form in E. But because we need a singular verb form, D is out.

Leaves us with E, which seems to be the best fit.