No one________ in the classroom at that time. [ ]
A. was
B. is
C. were
D. are
答案:A
根据利息支付方式的不同,债券分为()。
A.付息债券
B.零息债券
C.信用债券
D.一次还本付息债券
E.贴息债券
在平面直角坐标系中,我们称横、纵坐标都为整数的点为整点,则方程2x2+y2=18所表示的曲线上整点的个数为( ).