练习：

　　1.that was scientists understanding of methane?

　　A)It was produced from plants.

　　B)It was not a greenhouse gas.

　　C)It was produced in oxygen-free environments.

　　D)It traps more heat than any other greenhouse gas.

　　2.To test whether plants are a source of methanethe scientists created

　　A)a oxygen-free environment.

　　B)an environment with the same concentration of oxygen as the Earth has.

　　C)a carbon dioxide-free environment.

　　D)an environment filled with the greenhouse gas

　　3.hich statement is true of the methane emissions of plants in the experiment?

　　A)The lower the temperaturethe higher the amount of methane emissions.

　　B)Living plants release less methane than dried plants at the same temperature.

　　C)When exposed to sunlightplants stop releasing methane.

　　D)The higher the temperaturethe greater the amount of methane emissions.

　　4.What of the following about methane is Not mentioned in the passage ?

　　A)Plants growing in soil release methane.

　　B)Plants growing in water release methane.

　　C)Soil microbes consume methane.

　　D)Microbes in plants produce methane.

　　5.What is the beneficial point of some microbes consuming plant-produced methane?

　　A)Methane becomes less poisonous.

　　B)methane is turned into a fertilizer.

　　C)Less methane reaches the atmosphere.

　　D)Air becomes cleaner

　　练习：

　　1.that was scientists understanding of methane?

　　A)It was produced from plants.

　　B)It was not a greenhouse gas.

　　C)It was produced in oxygen-free environments.

　　D)It traps more heat than any other greenhouse gas.

　　2.To test whether plants are a source of methanethe scientists created

　　A)a oxygen-free environment.

　　B)an environment with the same concentration of oxygen as the Earth has.

　　C)a carbon dioxide-free environment.

　　D)an environment filled with the greenhouse gas

　　3.hich statement is true of the methane emissions of plants in the experiment?

　　A)The lower the temperaturethe higher the amount of methane emissions.

　　B)Living plants release less methane than dried plants at the same temperature.

　　C)When exposed to sunlightplants stop releasing methane.

　　D)The higher the temperaturethe greater the amount of methane emissions.

　　4.What of the following about methane is Not mentioned in the passage ?

　　A)Plants growing in soil release methane.

　　B)Plants growing in water release methane.

　　C)Soil microbes consume methane.

　　D)Microbes in plants produce methane.

　　5.What is the beneficial point of some microbes consuming plant-produced methane?

　　A)Methane becomes less poisonous.

　　B)methane is turned into a fertilizer.

　　C)Less methane reaches the atmosphere.

　　D)Air becomes cleaner