None of us expected Mr．Johnson to _____ at the party．We thought he was still abroad．

A．turn in

B．turn on

C．turn up

D．turn over

开炼机混炼时需人工割胶作业，主要是（）。

A、散热

B、使配合剂分散均匀

C、防止堆积胶太多

D、清除障碍