Being exposed to sunlight for too much time will do harm to one's skin.(動(dòng)名詞結(jié)構(gòu)做主語(yǔ))
==When you are exposed to sunlight for too much time,it will do harm to your skin.（時(shí)間狀語(yǔ)從句）

主語(yǔ)是being exposed to sunsunshine,謂語(yǔ)是will do harm to,賓語(yǔ)是skin,for too much time是定語(yǔ).

皮膚被曬傷,所以選擇被動(dòng),所以是B或者D.但是D不能做主語(yǔ),因?yàn)樗懊媸莻€(gè)介詞,所以只能做狀語(yǔ).您好。形容詞是不是不能作主語(yǔ)？比如exposed？