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B is corrent. Normally, an acceptance is considered to be effective when sent by the offeree under the UCC as long as the acceptance was sent by a reasonable method. This rule can be changed if so stated in the offer. In this situation, Zen did not accept by the means specified in the offer and, therefore, the acceptance was not effective when sent and a valid contract was not formed.
A is incorrect. The offer did not require receipt of the acceptance within a specified time but rather that the acceptance by telegram be sent by a specified time.
C is incorrect. Although acceptance was sent within the time specified, the correct means was not used.
D is incorrect. Normally, an acceptance is considered to be effective when sent by the offeree under the UCC as long as the acceptance was sent by a reasonable method. This rule can be changed, however, if so stated in the offer.