expose to---------to sunlight for too much time will do harm

expose to
---------to sunlight for too much time will do harm to our skins.为什么这里横线处要填being done.
though 是连词还是介词?
_______ by many successful models available,more and more young Chinese are now considering their own business.
A.Inspiring B.Being inspired C.Having inspired D.Inspried
(2)When____with a strong enemy,they always retreated.
A being faced B facing C faced D being facing.