题干
— Sammy, do you like the grammar book?
—Oh, I love it very much because it is so practical.
A：interesting
B：perfect
C：useful
答案(点此获取答案解析）
C
— Sammy, do you like the grammar book?
—Oh, I love it very much because it is so practical.
A：interesting
B：perfect
C：useful
orange 
的展开式中第m项的系数为
，若
，则
="( " )