A proposal is not revoked by

A proposal can be revoked in several ways under the Indian Contract Act, 1872. However, the death of the offerer does not automatically revoke the offer if the acceptor is unaware of it and has already sent the communication of acceptance. Therefore, the offer remains valid in such a case.

Lapse of prescribed time: If a specific time is mentioned for acceptance, the offer is revoked once that time expires. (Option A)

Lapse of reasonable time: If no time is prescribed, and a reasonable period passes without acceptance, the offer stands revoked. (Option B)

Counteroffer: A counteroffer results in the original offer being revoked and replaced by a new offer. (Option D)

Since death of the offerer does not revoke the offer if the acceptor is unaware and has accepted it, Option C is the correct answer.