题目

--- Did you telephone Uncle Sam our plan for the Christmas holidays on his farm? --- Yes, he was happy about our arrival, and he eagerly asked when         .        A．has we arrived                                     B．we had arrived        C．were we arriving                                 D．we were arriving，其中、是常数，且满足，是否存在这样的、，使是与无关的定值.若存在，求出的值；若不存在，说明理由.