Consider the following DFA with $Q=\{q_0,q_1,q_2\}$ :

for $0i2,$ we have $(q_i,0)=q_i$

for $0i1,$ we have $(q_i,1)=q_{i+1}$

and finally, $(q_2,1)=q_0$

Then the language accepted by this DFA can be described as follows:

a$.$Strings with the number of ones divisible by $3$

b$.$ Strings with an even number of zeros

c$.$ Strings with an even number of ones

d$.$ Strings with any number of zeros