Don't be late again, _____ you will be punished. [ ]
A. because
B. but
C. or
D. though
答案:C
按要求解下列方程
(1)y2-2y-4=0(公式法)
(2)2x2-3x-5=0(配方法)
(3)(x+1)(x+8)=-12.
煤氧化后,燃点(),使煤堆容易自燃。
A.降低
B.升高
C.不变
D.无法判断