In a critical period, development is _____________ to that period, and if it doesn't happen in that time frame it _____________; In a sensitive period, development is _______________ to that period, and if it doesn't happen in that time frame, it ____________. 

a. exclusive, never will; not exclusive, can be acquired in the future 

b. not exclusive, can be acquired in the future; exclusive, never will 

c. not restricted, never will; restricted, never will 

d. not specific, can be acquired later; very specific, is lost forever