Under Sections 3 to 5 of the Indian Contract Act, 1872, where an acceptance is sent by post, the communication of acceptance is complete as against the proposer -

Section 4 of the Indian Contract Act, 1872 provides that the communication of an acceptance is complete, as against the proposer, when it is put in a course of transmission to him so as to be out of the power of the acceptor, that is, when the letter of acceptance is posted. As against the acceptor, communication is complete only when the letter comes to the knowledge of the proposer. Section 5 complements this by prescribing when proposals and acceptances may be revoked. A mere decision or the signing of the letter does not complete acceptance, and delivery to the proposer governs the acceptor's position rather than the proposer's. The posting rule therefore makes the second option correct.