杠杆的平衡条件是：_________．某杠杆动力臂为阻力臂的4倍，用100牛的力最多可撬动_________牛的物体，此杠杆是_________杠杆．

Communication protocols are (66) connection-oriented or connectionless, (67) whether the sender of a message needs to contact and maintain a dialog with the recipient or (68) send a message without any, prior connect and with the hope that the recipient receives everything. (69) .These methods (70) the two ways that communication is implemented on networks.

A．make known

B．disclose

C．reveal

D．discover