Paper bags tend to keep the ethylene in，but they allow oxygen and ethylene to pass through

　　slowly.Plastic bags do not allow the free flow of oxygen or ethylene.In this experiment，the

　　green banana in paper bag with the ripe banana should ripen most quickly.The green bananas in

　　the paper bag should ripen faster than the bananas in the plastic bag.The banana left exposed to

　　air has an unlimited supply of oxygen，so it will turn brown most quickly.You will notice that

　　the side of this banana that rests on the counter will ripen more quickly than the other sides，because it has the closest contact (接触) with its own ethylene.The banana that is tightly wrapped in plastic has no oxygen supply and should ripen most slowly.Now can you see why bananas are sealed in plastic in many supermarkets?

　　【解题导语】　香蕉的成熟需要一定的过程，但是，其成熟过程受环境的影响，那么如何能知道香蕉的成熟过程呢？科学实验表明香蕉的成熟过程受环境的影响很大，因此，在不同的情况下，可以通过人为的作用来加速或减缓其成熟过程。

　　1．What makes the green banana in Bag 2 ripen more quickly than the ones in Bag 1?

　　A．Ethylene from the very ripe banana.

　　B．The free flow of oxygen or ethylene.

　　C．CO2 from the very ripe banana.

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