库仑定律的表达式。
参考答案：
砂土：τf=σtanφ 粘性土：τf=σtanφ+c
She was fortunate ______ to star in the film which ______ in the remote mountainous village.
A．having been picked out; was set
B．to have been chosen; set
C．to be picked out; was set
D．to have been chosen; was set
产褥期异常的临床表现是
A．产后4天，仍为血性恶露
B．产后12小时体温37.8℃
C．产后15天，宫底于耻上一指可及
D．产后3天下腹阵痛，有时需服止痛药
E．产后4天，双侧 * * 胀痛明显
