Which of the Following Is a Valid Tender Offer Rule

Which of the following is a valid tender offer rule?

A) The offer cannot be closed after 20 business days after the commencement of the tender offer.
B) The offer cannot be extended if the tender offeror increases the number of shares it will take or the price it will pay for the shares.
C) Any increase in price paid for shares tendered must be offered to all shareholders, including those who have previously tendered their shares.
D) A shareholder who tenders his or her shares loses the right to withdraw them prior to the closing of the tender offer.