A．They had plenty of time to get to the forest.
B．They kept their boat in the centre of the river.
C．The river carried their boat along quite quickly.
D．They had pushed off the bank.

A．Because the living expenses for each individual family are higher.
B．Because they believe people like to live in houses with gardens.
C．Because it involves higher cost compared with the building of houses.
D．Because the disposal of rubbish remains a problem for those living in flats.