When we got to the city center, ______shops were still open, but most of them were closed.
Don’t _____ your hands from the window when you are on a bus.
Maria has _____ trouble _____ math, so she often asks her math teacher for help.
Teachers should _____ their students to practice _____ English as much as possible.
China takes the leading position _____ space industry.
I spend much money on books _____ I am not rich.