As the idea of low­carbon life is now ________ accepted, more and more people   travel by public transport.

The driver got out of the car_______it caught fire .

They have held three meetings this week _________.

We often say that something is “as light as air”, but air is＿＿＿light. 

To children, good habits do not come        , so parents and teachers need to be their role models.