侧腭杆离开龈缘应()
A.8mm
B.至少6mm
C.4~6mm
D.3~4mm
E.1.5~2mm
参考答案:C
已知m、x、y满足:
(1)(x-5)2与|m|互为相反数,求x,m的值;
(2)-2aby+1与4ab5是同类项,求代数式:(2x2-3xy-4y2)-m(3x2-xy+9y2)的值.
—Miss Li, must we hand in our homework right now?
—No, you ____.You can hand it in tomorrow.
A.don’t
B.mustn’t
C.needn’t
D.may not