Observe the following incomplete letter sequence carefully:
 a a _ b c c _ a b b c _ a a b b _ c
A specific pattern governs the order and repetition of the letters. Choose the option that best fills the blanks (in order) to complete the sequence logically and symmetrically. ​​​​

​Given: a a _ b c c _ a b b c _ a a b b _ c
Now, we check each options.
​Option (a): c a b b
a a c b c c / a a b b c b / a a b b b c
​Option (b): a c b b
​a a a b c c / c a b b c b / a a b b b c
​Option (c): b a c c
​a a b b c c / a a b b c c / a a b b c c
​(It is a logical repeating pattern.)
​Option (d): b a a c
​a a b b c c / a a b b c a / a a b b c c
So, the following pattern is: a a b b c c
Thus, correct option is (c). ​​​​​​​​​​