Which of the ff. sequences are arithmetic sequences? 
a.) 15 , 11 , 7 , 3,...
b.) -6,-4,-1,3,...
c.) 0.3 , 1.3 , 2.3 , 3 , 3,...
d.) 1,2,3,4,...
e.) 5 , 10 , 16 , 23
f.) 1 , 3 , 5 , 7