On 4 July a client, a book publisher, received an inquiry from a university professor about the availability and cost of some textbooks. The publisher immediately made an offer by letter to the professor to supply the textbooks from available stock at a discounted price of £10 per book. The publisher asked for an early reply. The letter was delayed in the post and was received by the professor at 9.30 am on 9 July. Upon receipt, the professor immediately telephoned the publisher to accept the offer and was told that the offer had been revoked by email on 5 July. On hearing this, the professor checked his email account and found that the email had arrived but was one amongst many received that day and had not been read. The professor insists that his acceptance of the offer is valid and that the contract must be performed. The client seeks his solicitor's advice about whether the professor is .Is the professor that his acceptance of the offer is valid and that the contract must be performed?
选项：

A: Yes, as the offer was accepted before revocation of the offer was communicated to him.
B: No, as he failed to respond to the offer at the earliest and the offer lapsed for non-acceptance within a reasonable time.
C: Yes, as he was entitled to receive notice of revocation by letter as the offer was made by letter.
D: No, as the letter sent on 4 July was an invitation to treat.
E: No, as the revocation of the offer was made prior to his purported acceptance.