KTC切丝机正常生产时，当来料发生变化时，油缸液压部分的油压和流量（），刀门高度随之变化。
A、随之变化
B、增大
C、减小
D、不变
参考答案：D
抛物线y=x2+bx+c向上平移2个单位，再向左平移4个单位，得到抛物线y=x2，则b与c的值分别为（ ）
A．6，4
B．-8，14
C．-6，6
D．-8，-14
A number of books ______ been stolen from the library since the beginning of this term and the number _____ as large as 500.
A．have; are
B．has; is
C．has; are
D．have; is
