Let f(x) =[n+p sin x],x belongs to (0,π),n belongs to Z ,p is a prime number and [x] is greatest integer less than or equal to x .The number of points at which f(x) is not differentiable is
A. p
B. p-1
C. 2p+1
D. 2p-1
Let A = {x such that x belongs to N and x+1 < 8} and B = {x such that x belongs to N and x+3≤5}. Then find A union B?