在方块图中，对两个或两个以上信号进行代数运算的点称作（）。
A．信号线
B．引出点
C．方块
D．比较点
参考答案：D
There is still a long way to go to solve all the problems ______ conservation of natural resources.[ ]
A. concerning
B. concerned
C. concerning about
D. concerned about
He often borrows money ________ others, but he doesn’t lend anything _ ________ anybody.
A．from;from
B．to;from
C．from; to
D．to;to
