Plastic bags won’t be allowed to be used for free in the supermarkets. They can’t _________ easily, which does great harm to our environment.
It’s said that this kind of plant only gives off this strange perfume on ________ conditions which the scientists are trying to figure out now.
As we know, success often comes after ______ failure; so don’t be so upset about _______ failure of this matter.
不填; the
不填; a
It was in the street _______ I met one of my friends yesterday.
The beauty of the city is _______ my description.
You can't imagine what great trouble I had _______ his address.