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The upper timberline, like the snow line, is highest in the tropics and lowest in the Polar Regions. It ranges from sea level in the Polar Regions to 4,500 meters in the dry subtropics and 3500-4500 meters in the moist tropics.Timberline trees are normally evergreens, suggesting that these have some advantage over deciduous trees （those that lose their leaves） in the extreme environments of the upper timberline.There are some areas, however, where broad leaf deciduous trees form the timberline. Species of birch, for example, may occur at the timberline in parts of the Himalayas.

This paragraph supports which of the following statements about deciduous trees?

A.They cannot grow in coldclimates.

B.They do not exist at the uppertimberline.

C.They areless likely than evergreens to survive at the upper timberline.

D.They do not require as much moisture as evergreens do.