If s is a string over (0+1)*. Which one of the following languages is not regular?
A. L = {s ϵ {0, 1}* | n0(s) is a 3-digit prime}
B. L = {s ϵ {0, 1}* | for every prefix s' of s, |n0(s')-n1(s')| <= 2}
C. L = {s ϵ {0, 1}* | |n0(s)-n1(s)| <= 4}
D. L = {s ϵ {0, 1}* | n0(s) mod 7 = n1(s) mod 5 = 0}