用数字0，1，2，3组成无重复数字的四位数，这样的四位数的个数为（　　）

A．24

B．18

C．16

D．12

Many students do not like tostudy history(历史)．They say that there are (41) many names and dates to (42) ．But if we do not know about the (43) ，we can not understand the present well．For example，if we wish to know how men (44) to use fire，we have to know what men did (45) the past to travel at night or to keep themselves (46) in cold nights．Only a study of history will make US realize(意识到) (47) everything we do today is the result of what (48) people did in the past．

[A] read [B] make [C] write

As we (49) history，we learn many interesting (50) ．History helps US understand our present life better．