8.Only by shouting at the top of his voice _______ .

A．was he able to make himself heard

B．he was able to make himself heard

C．was he able to make himself hear

D．he was able to make himself hear

奴隶制作为最惨无人道的压迫制度，其显著的特点是（）。

A.剥削奴隶

B.根本不把奴隶当人看

C.把战俘作为奴隶

D.给奴隶套上无形的精神枷锁