"They are operating under incredibly difficult circumstances right now.

VOA: standard.2010.06.11

There may be circumstances under which it's the case but it's often difficult to control.

可能在某些环境下可以做到,但是通常情况下很难控制。

麻省理工公开课 - 热力学与动力学课程节选

There may be circumstances under which it's the case but it's often difficult to control.

可能在某些环境下可以做到,但是通常情况下很难控制。

麻省理工公开课 - 热力学与动力学课程节选