26. Mr. Green has two sons, one of _____ working as a bus driver now.
It worries the couple a lot ______ their only son is behaving worse and worse these days.
People generally think that fairness and justice are at the centre of ______ they are striving for.
______ once every two years, whether it is a car, a bus or a lorry, is the rule that all drivers must obey in our country.
In extreme weather, a worn tyre can break easily ______ it’s mended, as is often the case.
Of all the clues they provided, ______ is of any help for solving the case of robbery.