16. ________ girl in red has formed the habit of walking her dog at ____________ dusk every day.
A.A; / B.A; the C. The; / D. The; a
17. It is reported that the fire burned for quite some time______it was brought under control.
A.until B.when C.before D.once
18. English is a language that many people around the world________not speak perfectly but __________at least understand.
A. may;can B. would;might C. will;must D. should;might
