为保证衬砌应力量测中钢弦压力盒的工作质量，使用前应对其进行何种性能试验（）

A、钢弦抗滑性能试验

B、密封防潮试验

C、频率稳定性试验

D、振动试验

Questions 11 to 18 are based on the conversation you have just heard

A．The shipping company.

B．The firm dealing with documents.

C．The travel firm.

D．The firm with a lot of people.