At the meeting they discussed three different __________ to the study of

mathematics.

A．approaches

B．means

C．methods

D．ways

诊断气管异物最主要依据是（）

A.异物吸入史

B.咳嗽

C.呼吸困难

D.听诊肺呼吸音减弱

E.X线肺部阴影