半球内有一内接正方体，则该半球的全面积与正方体的全面积之比为( )。
参考答案：A
解析： 设正方体棱长为x，球半径为R，则
I _____ a dictionary. I _____ it in the bookshop near our school. [ ]
A. have bought, bought
B. have bought, have bought
C. bought, have bought
D. bought, bought
如何给备用泵换油？
