6. The factory has to stop working for a day _________ the machines can be cleaned.
| A．in case | B．supposing that | C．the moment | D．so that |
There are some health problems that, when ______ in time, can become bigger ones later on.
| A．not treated | B．not being treated | C．not to be treated | D．not having been treated |
He commanded that all the gates ________．
| A．should shut | B．would be shut | C．shut | D．be shut |
As is known to us all, English books of this kind ________ well in middle schools.
| A．sell | B．sells | C．is sold | D．are sold |
_______ everyone here, I wish you a pleasant journey back to your country.
| A．By means of | B．On behalf of | C．In search of | D．For fear of |
I think you need some outdoor exercise. Plenty of fresh air will ________good health.
| A．contribute to | B．devote to | C．apply to | D．adjust to |