Flowers are not intended by nature to live very long. Their biological purpose is simply to attract birds or insects, such as bees, for pollination（授粉）. After that, they quickly dry up and die. The process by which flowers consume oxygen and produce carbon dioxide（二氧化碳）, called respiration（呼吸）, generates the energy the flower needs to give the flower its shape and color. The making of seeds also depends on this energy. While all living things respire, flowers have a high level of respiration. A result of all this respiration is heat, and for flowers the level of heat relative to the mass of the flower is very high. Respiration also brings about the eventual death of the flower. Thus the greater the level of respiration, the sooner the flower dies.
Respiration plays a key role__________.
A、by keeping its original shape and color
B、in the life of cut flowers
C、to produce carbon dioxide
D、for as long as possible
【答案解析】 可以通过短语的固定搭配选择plays a key/important role in …“在某方面起重要的作用”；因此选择B。