Of the following examples, the least questionable negotiating tactic is

a. a party says he needs time to think about a proposal and promises to get back to you early the next day.

b. a party tells you that an agreement must be reached today or he cannot guarantee the settlement amount agreed to will be available tomorrow.

c. as negotiations appear to have concluded, a party apologizes and says he neglected to mention a particular item and would like to discuss it.

d. a party says, as you appear to be close to agreement, “Why don’t we split the difference?”