螺杆泵运转时，螺纹作螺旋线运动，又是连续的，因此，从螺杆槽排出的液体比齿轮泵均匀。
参考答案：错
The old pictures bring them to the days ______they spent together, ____life was hard but happy.
A． when, whose
B．which, whose
C．which, when
D．when, which
