A painter has painted one-third of a rectangular wall which is ten feet high. When she has painted another 75 square feet of wall, she will be three-quarters finished with the job. What is the length (the horizontal dimension) of the wall ？（）

A.18 feet

B.12 feet

C.10 feet

D.9 feet

E.6 feet

人类便于取用的河水、湖水及浅层地下水等淡水大约占水圈总水量的

A．0.01%

B．0.2%

C．1.0%

D．5.0%

E．12.0%