单项选择题

The passage is mainly concerned with the ______.

A．geographical distribution of plant and animal species
B．location and purpose of the pulvini
C．appearance of the mimosa
D．process that causes movement in the mimosa

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单项选择题

According to the passage, the sensitive plant's leaves move quickly when parts of the pulvini ______.

A．drop off
B．become limp
C．revolve
D．twitch

单项选择题

Argonne believes that people should regard maglev transportation as ______.

A．safe, efficient high-speed trains
B．the most exciting form of transportation for the future
C．a kind of aircraft
D．the most economical form of transportation