China's icebreaker Xuelong  ______  by heavy floes since Friday after rescuing passengers on a Russian vessel stranded in Antarctica.

A．has been trapped

B．had been trapped

C．has trapped

D．was trapped

常见的凹凸压印机的底板是（）。

A.塑胶底板

B.金属底板

C.橡皮底板

D.石膏底板