`- - aba - - ba - ab`

Options

A. abbba
B. abbab
C. baabb
D. bbaba

Explanation

To solve the sequence `- - aba - - ba - ab`, we need to identify a pattern that can be used to fill in the blanks with A's and B's.

### Step-by-Step Solution:

1. **Identify the Given Sequence**: The sequence provided is `- - aba - - ba - ab`. We need to fill in the dashes with A's and B's.

2. **Analyze the Existing Pattern**:
- The existing letters are `aba`, `ba`, and `ab`.
- We can observe that there is a repetition of A's and B's.

3. **Look for a Repeating Pattern**:
- If we analyze the existing letters, we can see that the sequence seems to alternate between A's and B's.
- The pattern appears to be `A, B, A, B, A, B, A, B, A, B`.

4. **Fill in the Blanks**:
- Starting from the left, we can fill in the blanks:
- The first two dashes can be filled with `A` and `B` respectively.
- The next letters are `aba`, which fits the pattern.
- The next two dashes can again be filled with `A` and `B`.
- The next letters are `ba`, which also fits the pattern.
- The next dash can be filled with `A`.
- The last letters are `ab`, which fits the pattern.

5. **Final Sequence**:
- After filling in the blanks, the complete sequence becomes `A B A B A B A B A B`.

### Conclusion:
The filled sequence is `A B A B A B A B A B`, confirming that the pattern is consistent throughout.