Now it’s been possible for us to be taken into “space”, we can experience weightlessness for a short time.

On rainy days, accidents _____ happen sometimes on steep roads.

The ________ working age in western countries is usually 14 to 16 , depending on the number of hours and type of work. [ ]

past half-century, average incomes _______ quickly indeveloped countries, yet happiness levels have remained almost the same.

We should get prepared for dealing with________problems_________.