绿色植物进行光和作用时，吸收和释放的气体分别是（　　）

A．O₂CO₂

B．CO₂ N₂

C．N₂CO₂

D．CO₂O₂

Is it the days __________you studied in our school ________have a great effect on your maths?

A．that, where

B．that, that

C．when, where

D．when , that