几道高中英语单选,

几道高中英语单选,
1.Some people haven't realised sth ao common as_____ to the sun for a long time will do harm to their skin and even cause skin cancer.
A.exposing B.exposed C.having exposed D.being exposed
2.It is sad to see the old museum being _____ to make way for a new shopping center.
A.taken in B.taken down C.taken up D.taken out
3.-Where have you been all day?
-I ____ my old friend and we have been talking until just now.
A.met B.have met C.have been meeting D.had met
4.The past decade ___ great changes in my hometown,where you can see many new buildings___here and there.
A.witnessed; was sprung up B.has witnessed; have been sprung up
C.has witnessed; have sprung up D.witnessed; sprung up