Pattern Recognition - 108

Find out the next two letters in the series.
a , b , e , c , i , d , o , _ , _ ,.................................

Answer

a , b , e , c , i , d , o , _ , _ ,.................................

Vowels       - a, e , i ,o , ............. Next letter - u
Consonants - b, c , d , ................ Next letter - f

Next two letters in the series u ,f

a , b , e , c , i , d , o , f , u ,.................................