A:2,π
B:2,4π
C:,π
D:,4π
I got on the bus and found a seat near the back, and then I noticed a man ____ (sit) at the front.
在做胸部的X光检查过程中,医生要求你吸气后闭气不动,吸气过程中你的肋骨和膈的运动方式是( )