既有损失机会又有获利可能的风险是（）
A.自然风险
B.投机风险
C.纯粹风险
D.财产风险
参考答案：B
The letter ______ three days ago and it ______ yesterday. [ ]
A. had post, had arrived
B. was posted, arrived
C. posted, arrived
D. had been posted, was arrived
