发生颈部淋巴结转移率最高的头颈恶性肿瘤为()
A.喉癌
B.下咽癌
C.鼻咽癌
D.环后癌
E.扁桃体癌
参考答案:C
分解因式:
(1)2x2-x;
(2)16x2-1;
(3)6xy2-9x2y-y3;
(4)4+12(x-y)+9(x-y)2.
Overall, it is going to become much easier for people to communicate () the Net Communicating with others in real time will soon be the norm.
A.by
B.in
C.over
D.onto