Step 1: Understanding the concept of revocation of proposal.
Under the Indian Contract Act, 1872, the proposer (the person who makes the offer) may revoke his proposal at any time before its acceptance is communicated to him, but not after the communication of acceptance is complete as against him.
Step 2: Relevant section.
Section 5 of the Indian Contract Act, 1872 specifically states that —
“A proposal may be revoked at any time before the communication of its acceptance is complete as against the proposer, but not afterwards.”
Step 3: Conclusion.
Hence, the correct section that defines revocation of proposal is Section 5 of the Indian Contract Act, 1872.