当a=-5，b=-6时，代数式a2+b2=（ ）。
61
SDH信号最基本的模块信号是()。
A．STM-0
B．STM-1
C．STM-3
D．STM-4
He ____ the cave before the police arrived, but he failed.
A．managed to flee away from
B．tried fleeing out of
C．managed fleeing
D．tired to flee
