__________ entered the office when he realized that he had forgotten his report.

A．He hardly had

B．Had he hardly

C．Hardly had he

D．Hardly he had

润滑油的（）是保证提供足够润滑油量的特征参数，保证了压缩机平稳运行。

A.温度

B.压力

C.粘度

D.闪点