设a与b都是常数，且b＞a＞0．
设S所围成的实心环的空间区域为Ω，计算三重积分[*]
参考答案：利用柱面坐标计算．
Mike has much difficulty ________ Chinese so he often asks me ________ help.
A．to understand, with
B．understanding, of
C．to understand, for
D．understanding, for
* * 对马克思列宁主义关于人类社会历史发展规律的表述是怎样概括的？
