He is______an important customer now and he will be back tonight.
A. calling on
B. calling up
C. calling at
D. calling for
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湖南道县玉蟾岩遗存中发现的水稻稻粒,是目前所知世界上最早水稻标本。()
Some poor families can not afford the tuition______of their children.
A. fees
B. payments
C. fares
D. costs