入射光强度为透射光的100倍时，照片密度值应为

A．0.1
B．0.2
C．1.0
D．2.0
E．3.0

小题1:Trees can get light from       in the daytime.

A．C0₂

B．O₂

C．the sun

D．the moon小题2:Chlorophyll is in         .

A．sunlight

B．soil

C．air

D．leaves小题3:We can get more O­₂ by         .

A．planting more trees

B．cutting trees down

C．making the water in soil(土壤) polluted

D．making more CO₂小题4:CO₂ from air and      can produce food  for trees with the help of chlorophyll and sunlight.

A．water in the sea

B．water from soil

C．water in the river

D．O₂ into air小题5:The picture tells us         .

A．how trees let O₂ go into air in the sunlight

B．how trees let CO₂ go into air in the sunlight

C．the sunlight isn't important to trees at all

D．trees can take in O₂ and let out CO₂