Where in the passage does the author compare the energy consumption of skyscrapers with that of a city

A．The exterior surrounding air is heated.
B．The windows must be cleaned daily.
C．Construction time is increased.
D．Extra air-conditioning equipment is needed.

A．The noise from their construction.
B．The removal of trees from building sites.
C．The harmful effects on the city's grass.
D．The high cost of rentable office space.