IMO supposed = adjective.
supposedly = adverb.

Mediterrarian predecessors = noun phrase....

so we need to have supposed.

sogmat wrote:\Carbon-14 dating reveals that the megalithic monuments in Brittany are nearly 2,000 years as old as any of their supposed Mediterranean predecessors.
(A) as old as any of their supposed
(B) older than any of their supposed
(C) as old as their supposed
(D) older than any of their supposedly
(E) as old as their supposedly

oa b

please explain supposed vs supposedly

please explain as old as vs older than

as old as is used to compare two things that are equal. In the sentence nearly 2,000...any indicates the monuments are not equal, that there's a contrast of "younger than" or "older than"; in this case, it's "older than".

In general we say:

I am 5 years older than my brother.

The woman is two times as old as her son.

2000 years so older than.

predecessors->Noun
Mediterranean->adjective

The sentence says the predecessors are mediterranean so its a fact as stated by the sentence so we need something to qualify the noun predecessors

supposed is an adjective qualifying predecessor
SUPPOSEDLY is an adverb which would qualify Mediterranean and in this sentence we have no doubt that they are mediterranean but if they are the predecessors so use "supposed"

B

Are we supposed to know that, just by reading the question, the Brittany monuments are logically older than the Mediterranean ones? Pardon my ignorance, but are there any words in the question that suggests that this is the case, or is this simply common sense?