some people have not realized something ak common as( ) to the sun for a long time

some people have not realized something ak common as( ) to the sun for a long time
some people have not realized something ak common as( ) to the sun for a long time will do harm to their skin and even causee skin cancer
A exposing B exposed C havingn exposed D being exposed 请大家帮忙分析一下句子成分以及选哪个答案的原因