下面几种情形中，不可能是线性规划数学模型的约束条件形式的是（）
A.=
B.＜
C.≥
D.≤
参考答案：B
–What was your brother doing at this time yesterday?
-- He was reading a magazine ________ I was writing an e-mail at home.
A．as soon as
B．after
C．until
D．while
资金池理财产品在出现巨额赎回时无法及时变现资产以兑付本金和收益的的风险是（）。
A.信用风险
B.市场风险
C.流动性风险
D.操作风险
