avg case unsuccessful linear search complexity

Question

Average case complexity of sequential search if the element that is searched is not in the list

a)  ( n+p) /2                        b)  (np+1)/2                

c)  n(1-p/2)+p/2                  d) n(1+p/2) +p/2

Comments

if a element is not present in the list then in each case we will search the entire list so avg case will be worst case=O(n) where n is number of element in the list..??