4 C
Being exposed to sunlight for too much time will do harm to one's skin.(动名词结构做主语)
==When you are exposed to sunlight for too much time,it will do harm to your skin.（时间状语从句）
1 Having waited in the queue for half an hour,Tom suddenly realized that he had left his wallet at home.(分词结构做时间状语)
===After he had waited in the queue for half an hour,Tom suddenly realized that he had left his wallet at home .（时间状语从句）