题目

-----How was your camping in the mountains last week, Joan? -----Oh, it was just a ___because we were woken up by a terrible storm at midnight. A. mess          B. nightmare      C. fun           D. pleasure 答案：B 解析: 略方程组x+y=1x+z=0y+z=-1的解是（　　）A．x=-1y=1z=0B．x=1y=0z=-1C．x=0y=1z=-1D．x=-1y=0z=1