Finish the following sentence with the best choice: How to whistle?

Choices:
- Purse your lips by putting them together tightly while curling your tongue under. Blow steadily as you breathe out.
- Purse your lips by putting them together tightly while curling your tongue over. Blow steadily as you breathe out.

Answer:
Purse your lips by putting them together tightly while curling your tongue under. Blow steadily as you breathe out.