Which sequence of letters when placed in the blanks one after the other will complete the given letter series ?
-aabb-abba-b

Options

A. bab
B. aba
C. bba
D. baa

Explanation

To solve the problem of completing the letter series "aabb-abba-b", we need to analyze the given sequence and identify the pattern. Let's break it down step by step.

### Step-by-Step Solution:

1. **Identify the Given Sequence**:
The sequence provided is: aabb - abba - b. We need to fill in the blanks represented by dashes.

2. **Analyze the Existing Patterns**:
- The first part is "aabb".
- The second part is "abba".
- The third part is "b".

3. **Look for Patterns**:
- Notice that the first two parts consist of combinations of 'a' and 'b'.
- The first part "aabb" can be seen as two 'a's followed by two 'b's.
- The second part "abba" can be rearranged to show that it contains two 'b's and two 'a's but in a different order.

4. **Check the Options**:
We have four options to fill in the blanks:
- Option 1: b a b
- Option 2: a b a
- Option 3: double b a
- Option 4: b double a

5. **Testing Each Option**:
- **Option 1 (b a b)**: If we place "b a b" in the blanks, we get "aabb - abba - b a b". This does not maintain a consistent pattern.
- **Option 2 (a b a)**: If we place "a b a", we get "aabb - abba - a b a". This also does not maintain a consistent pattern.
- **Option 3 (double b a)**: If we place "double b a", we get "aabb - abba - double b a". This does not fit the pattern.
- **Option 4 (b double a)**: If we place "b double a", we get "aabb - abba - b a a". This maintains the pattern of alternating 'a's and 'b's.

6. **Conclusion**:
The correct option that completes the sequence while maintaining the established pattern is **Option 4: b double a**.

### Final Answer:
The sequence of letters that will complete the given letter series is **b double a**.