A、Because city-dwellers are obliged to adopt a wholly unnatural way of life. B、Because the sun was hidden from view by tall buil

Large modern cities are too big to control. They impose their own living conditions on the people who inhabit them. City-dwellers are obliged by their environment to adopt a wholly unnatural way of life. They lost touch with the land and rhythm of nature. It is possible to live such an air-conditioned existence in a large city that you are barely conscious of the seasons. A few flowers in a public park(if you have the time to visit it) may remind you that it is spring or summer. A few leaves clinging to the pavement may remind you that it is autumn. Beyond that, what is going on in nature seems totally irrelevant. All the simple, good things of life like sunshine and fresh air are at a premium. Tall buildings blot out the sun. The traffic fumes pollute the atmosphere.
    Even the distinction between day and night is lost. The flow of traffic goes on unceasingly and the noise never stops.