"Environmentally friendly" (Line 2, Para. 4) is closest in meaning to ______.

A．the London citizens
B．those who commute to London from other places
C．managers who are anxious about their staff getting to work
D．passengers who make complaints

A．overpopulation causes the problems in cities
B．two-thirds of the world' s population are living in cities today
C．it isn' t difficult to solve the problems faced by cities today
D．with fewer people, we would be free from any problems