当发现主机个别缸有拉缸现象时，应立即（）。
A.停车
B.加强冷却
C.降速
参考答案：C
若把二次函数y=x2-2x-3化为y=（x-h）2+k的形式，其中h，k为常数，则h+k=（ ）。
The retired workers were invited to the company,________surprise,changes had been so great over
the years. [ ]
A. whose
B. who
C. to whom
D. to whose
