There are a lot of reasons ------- pollution,such as factory

There are a lot of reasons _______ pollution,such as factory wastes,andtrees cutting.   
 A) of              B)  in              C)  for             D)  at  
Who is _________ of the twins?
A)younger      B)the younger C)youngest   D) the youngest 
How long will your boss be ________?
A)away           B)far              C)back             D)of 
No agreement was reached in the discussion as neither side would give way to _________?
A)the other    B)any other    C)another       D)other 
Maybe I'll fall asleep before my father gets home.fall asleep means__________?
A)go to bed  B)go to sleep   C)feel sleepy  D)have a rest