—Why are there so many policemen in the park?
—They are trying ________ a missing girl.
A:search
B:to search
C:search for
D:to search for
— About twenty minutes' ride.
情绪从一定意义上说是心灵的“窗户”,因为()
已知 {x=2y=1 是方程kx-y=3的解,那么k的值是( )