重力坝主要依靠坝体自身重量产生的抗滑力来满足坝体的稳定要求。（）
参考答案：对
In face of trouble, although I feel disappointed about where I am, I still think _______ about where I am going.
A．optimistically
B．controversially
C．conventionally
D．alternatively
临界分切应力
