While Rose ______ for the lift, she is listening a recording about the Eiffel Tower. A. waits B. is waiting C. has waited D. will wait 答案:B短周期元素X、Y、Z、M、R在周期表中的相对位置如图所示。下列说法正确的是 XY Z MR A.X的气态氢化物比Y的气态氢化物稳定B.原子半径的大小顺序为:r(R)>r(M)>r(Z)C.元素的最高价氧化物对应水化物的酸性R强于MD.离子R-和Z 3+的电子层结构相同