问题补充：
. the sunlight for a long time is harmful to your skin.
A. Exposed to
B. To expose in
C. Exposing in
D. Being exposed to
答案：
A. Exposed to
B. To expose in
C. Exposing in
D. Being exposed to
解析：动名词短语做主语。Be exposed to..暴露在…遭受…；句意：长时间暴露在阳光下对你的皮肤有害。B项不定式表示具体的一次性的行为。故D正确。
