Under the Inland Navigation Rules, two power-driven vessels reach a passing agreement by radiotelephone before exchanging whistle signals. Which statement correctly describes their obligations under Rule 34?

1. A. They are still required to exchange whistle signals because radiotelephone agreement does not satisfy Rule 34
2. ✓ They are not obliged to sound the whistle signals prescribed by Rule 34, but may do soCorrect
3. C. They must sound the whistle signals prescribed by Rule 34 as confirmation of the radiotelephone agreement
4. D. Only the give-way vessel is relieved of the obligation to sound whistle signals