题目

If you are unable to attend the interview, for        reason, you should inform us immediately. A. no matter what                                   B. whatever                  C. however                                        D. no matter how 答案：BX、Y、Z为短周期元素，这些元素原子的最外层电子数分别为1、4、6，则由这三种元素组成的化合物的化学式不可能为 [　　] A．XYZB．C．D．