'X' made an offer to 'Y', which 'Y' accepted. But before acceptance came to the knowledge of 'X', 'Y' canceled his acceptance telegram. When will this cancellation be complete?

• A. when the wire is sent
• B. When the subject matter of the wire came to the knowledge of 'X'
• C. When 'X' approves the cancellation
• D. When wire 'X' is received by