Study the following arrangement of the English alphabet and answer the questions given below:
P M S K Q A B M N O P Q R W
If letters at even positions are replaced by a succeeding letter and letters at odd places are replaced by a preceding letter, then which letters will be twice in number in the new series?1
O, N and P
2
O and P
3
O, N, R and P
4
O, N, R, B and P