Answer:

1. **No one should know the details of our plan. (SECRET)**

  - **Secret** details of our plan should not be known by anyone.

2. **He always gets what he wants because he is very polite. (THANKS)**

  - He always gets what he wants **thanks** to his politeness.

3. **I will not be able to fly to New York on Wednesday. (TO CANCEL)**

  - I will have **to cancel** my flight to New York on Wednesday.

4. **I had only just arrived home when the phone rang. (SOONER)**

  - I had **sooner** arrived home when the phone rang.

5. **It’s all a matter of money, in the end. (COMES)**

  - In the end, it all **comes** down to a matter of money.

Explanation:

1. **No one should know the details of our plan. (SECRET)**

- **Secret** details of our plan should not be known by anyone.

2. **He always gets what he wants because he is very polite. (THANKS)**

- He always gets what he wants **thanks** to his politeness.

3. **I will not be able to fly to New York on Wednesday. (TO CANCEL)**

- I will have **to cancel** my flight to New York on Wednesday.

4. **I had only just arrived home when the phone rang. (SOONER)**

- I had **sooner** arrived home when the phone rang.

5. **It's all a matter of money, in the end. (COMES)**

- In the end, it all **comes** down to a matter of money.