下列地质剖面图中的A、B、C、D四处，属于向斜构造的是
A、A
B、B
C、C
D、D
答案：B
—How was the dinner last night?
—It was OK, but I made a mistake . I____ arrive at 7:00,but I arrived at 8:00.
A．was willing to
B．was supposed to
C．was allowed to
D．was used to
计算：（x+3y）（x-3y）=______．
