To my knowledge,-to sunlight in Hainan Will Surely Burn Your

eing exposed to sunlight 相当于充当一个主语,要用进行时。如swimming is my favorite sport。用swimming,而不用swim。a选项为分句,不能充当主语,after having been exposed,your skin will be burned。c选项为被动形式也不能充当主语,又不能用exposing,因为意思为被暴露在,只有加上be动词再加ing,才能充当主语。d的话,没有加having的必要,如有应为having been exposed to sunlight for three hours,my skin has been burned。