19. _______ rich one may be there is always something one wants.
How long do you think it will be ________ the computer company puts forward a new product?
The famous scientist, _______ a dinner party will be held tonight,is to arrive soon.
__________twice a year, whether it is a car or bus or a truck, is the rule that every driver must obey in this city.
--- An ant has two stomachs --- one for itself, one for others. --- Really? Quite interesting. I ____ anything about it.
AIDS is said__________the biggest health challenge to both men and women in that area over the past few years.