下列是普通黄铜的是（）。
A、H68
B、QSn4-3
C、QBe2
参考答案：A
已知双曲线2x2-3y2-6=0的一条弦AB被直线y=kx平分，则弦AB所在直线的斜率是_________________.
Each of the students, working hard at his or her lessons, _____ to go to university. [ ]
A. hope
B. hopes
C. hoping
D. hoped
