Which of the following is an exception to the Mailbox Rule?

The rationale for the answer lies in the Mailbox Rule, which states that an acceptance of an offer is generally effective when it is sent, rather than when it is received by the offeror. However, there are exceptions to this principle. In this case, the assertion that an acceptance becomes effective only when received indicates a situation where the Mailbox Rule does not apply.

This may occur in particular contractual scenarios, or in situations where the offeror specifies that acceptance must be communicated directly or received to take effect. For example, if an offer specifies that the acceptance must be physically delivered to a certain location or communicated in a specific manner, then acceptance would only be effective upon receipt, making this option an exception to the general rule.

By contrast, the other options do not accurately reflect exceptions to the Mailbox Rule. The idea that any offer can be revoked at any time, while true in principle, does not directly relate to the conditions of an acceptance's effectiveness. Similarly, requiring acceptance to be done in person or demanding that all communications must be documented does not specifically address the circumstances that alter the effectiveness timing of an acceptance. Consequently, the second option accurately highlights when the Mailbox Rule does not apply regarding the timing of an acceptance.