什么叫井壁压力梯度？
参考答案：
井壁压力梯度是指天然气从地层内流到井底时，在紧靠井壁附近岩石单位长度上的压力降。
蚂蚁等昆虫的足是______的，依靠足部______的收缩和舒张，使分节的足产生运动．运动时，一般以一侧的______和另一侧的______为一组，进行交替运动．
Jenny ________ a rich man. She has ________ him for 5 years.
A．married with; married with
B．married, been married to
C．married to; been married
D．married; married
