减去2-x等于3x2-x+6的整式是[ ]
A.3x2-2x+8
B.3x2+8
C.3x2-2x-4
D.3x2+4
答案:A
In the past few months, the country _____ a further tightening of supply restrictions, making fuel and food supplies more difficult to obtain.
A.would witness
B.witnesses
C.has witnessed
D.had witnessed
调节保证计算的实质是什么?