In my opinion, the key ____air pollution is to inspire people to take public transport in big cities.

How could they keep us waiting for so long? — They got on the bus half an hour ago and they ________ be here in ten minutes, I think.

Electric trains have now _______ steam trains in England.

­­­So you missed the meeting.—­­­____. I got there ten minutes before itfinished.

It ______ that Tokyo will be the host city for the2020 Summer Olympic Games