Here are the answers for the /b/ or /p/ sound for each underlined letter:

0. plenty - **p**
1. bubbles - **b**
2. beautiful - **b**
3. picnic - **p**
4. ponytail - **p**
5. please - **p**
6. panda - **p**
7. between - **b**
8. goodbye - **b**
9. parents - **p**
10. plate - **p**
11. play - **p**
12. bean - **b**
13. well-built - **b**
14. happy - **h**
15. airport - **p**