答案:B
A、 x2+y的分母是2,不含字母,所以它不是分式;故本选项错误;
2
故选:B.
It is clever _________ you _________ out the problem. [ ]
A. for; to work
B. of; working
C. to; working
D. of; to work
在铜互连中,为什么要用铜扩散阻挡层?阻挡层分成哪几种,分别起什么作用?