按风险发生的时间，可以将外汇风险划分为（）。
A.时间风险
B.交易风险
C.经济风险
D.价值风险
E.转换风险
参考答案：B, C, E
Mary is ill today. If she _____, she _____ absent from school. [ ]
A. were not ill; wouldn't be
B. had been ill; wouldn't have been
C. had been ill; should have been
D. hadn't been ill; could be
鱼类中含有的多不饱和脂肪酸主要是（）。
A.EPA和DHA
B.亚油酸和EPA
C.亚油酸和DHA
D.亚油酸和β－亚麻酸
E.α－亚麻酸和DHA
