--- It’s the fourth time that heavy smog(雾霾) has hit the city this month. --- It’s high time we _______ measures to fight air pollution.
The illness from which Mary is suffering has now been _____ as hepatitis (肝炎).
If the boy had _____ the dog alone it wouldn't have bitten him.
The generation _____ makes it difficult for parents to understand their children's opinions.
Despite their good service, most inns are less costly than hotels of _____ standards.
He was afraid that the branch might bend over and break, and he would be sent _____ to the ground.