1 . It has been c________ that the global space economy is increasing by billions of dollars every year. （根据首字母单词拼写）

2 . I c________ that the total cost for treatment would be $12500.（根据首字母单词拼写）

3 . With the development of technology,scientists now have no difficulty c_______the time when the spaceship will reach the moon.

4 . The scientists are able to accurately__________（计算）when the spaceship will reach the moon.

5 . Teaching year after year，he gradually ________much experience.

A．calculated	B．accumulated
C．abandoned	D．appointed