六年级有学生152人,五年级有学生148人,两个年级一学期平均每人画了18张水彩画。这些学生一学期一共画了多少张水彩画?
(152+148)×18=5400(张)
按期权买方行权时间划分,期权分为()。
A.看涨期权
B.看跌期权
C.欧式期权
D.美式期权
Brian puts the cardboard on top of the jar and _____. [ ]
A. turn over it
B. turn it over
C. turn them over
D. turn over them