`- st t - t t - t ts -`

Options

A. tsts
B. ttst
C. sstt
D. tsst

Explanation

To solve the given sequence `- st t - t t - t ts -`, we need to identify the pattern and find the appropriate term that fits into the sequence.

### Step-by-Step Solution:

1. **Identify the Sequence**:
The sequence provided is `- st t - t t - t ts -`. We need to analyze the terms to find a pattern.

2. **Break Down the Terms**:
Let's rewrite the sequence with placeholders for the missing terms:
- First term: `-`
- Second term: `st`
- Third term: `t`
- Fourth term: `-`
- Fifth term: `t`
- Sixth term: `t`
- Seventh term: `-`
- Eighth term: `t`
- Ninth term: `ts`
- Tenth term: `-`

3. **Look for Patterns**:
Observing the terms, we can see that:
- The first term is missing.
- The second term is `st`.
- The third term is `t`.
- The fourth term is missing.
- The fifth term is `t`.
- The sixth term is `t`.
- The seventh term is missing.
- The eighth term is `t`.
- The ninth term is `ts`.
- The tenth term is missing.

4. **Finding the Missing Terms**:
From the pattern, we can see that:
- After `st`, we have a single `t`.
- After the second `t`, we have another `t`.
- After the third `t`, we have `ts`.

This suggests a repetition of `t` and a gradual increase in the number of `t`s.

5. **Determine the Next Term**:
Following the pattern, we can deduce that the missing terms should also follow the established pattern. The missing terms seem to be repetitions of `TSSD` based on the video solution.

6. **Final Sequence**:
By adding `TSSD` in the missing places, we get:
- First term: `TSSD`
- Second term: `st`
- Third term: `t`
- Fourth term: `TSSD`
- Fifth term: `t`
- Sixth term: `t`
- Seventh term: `TSSD`
- Eighth term: `t`
- Ninth term: `ts`
- Tenth term: `TSSD`

### Conclusion:
The appropriate term to fill in the sequence is `TSSD`. Therefore, the answer is option D, which is `TSSD`.