Here's the
official explanation provided by the GMAC for this question:
This sentence discusses tartans allegedly worn since antiquity. In context,
since antiquity indicates that the wearing of the tartans allegedly started in the distant past and was or is still continuing at the time of the allegation. An appropriate verb form to convey this meaning is the present perfect passive
to have been worn. Option A: The present passive infinitive
to be worn is incompatible with the past-tense meaning conveyed by
since antiquity.
Option B: Correct. The present perfect passive infinitive
to have been worn correctly conveys the intended sense of an ongoing activity that allegedly started in the distant past and was or is still continuing at the time of the allegation.
Option C: The present passive
are worn is incompatible with the past-tense meanings conveyed by
were and
since antiquity.
Option D: The wording
alleged as having is unidiomatic. The preposition
as is not conventionally used to link the verb
to allege with the content of the allegation.
Option E: The present passive
are worn is incompatible with the past-tense meaning conveyed by
since antiquity.
The correct answer is B.
Please note that I'm not the author of this explanation. I'm just posting it here since I believe it can help the community.