Air is all round us．It is around us___31____we walk and play．From the time we are born，air is around us on every side．When we sit down，it is around us．When we go to bed．air is  32  around us．We live  33  air．
All living things  34  air．Living things cannot live  35   air．We can live without any water for  36  days，but we cannot live for more   37 a few minutes without air．When we are working  38  running，we need more air．When we are asleep，we need less air
We live in air but we cannot see it．We can only feel it．We can feel it when it is  39  ．  Moving air  40  wind．  

A．if B．because C．when D．what

A．too B．also C．either D．yet

A．with B．by C．in D．around

A．need B．hope C．want D．1ike

A．little B．a Iittle C．few D．a few

A．about B．over C．than D．then

A．or B．and C．so D．but

A．moving B．standing C．stopping D．sleeping

A．is 1ike B．1ikes C．calls D．is called