INLAND ONLY Vessels "A" and "B" are meeting on a river as shown in illustration D029RR below and will pass 1/4 mile apart. Which statement is TRUE?

Correct Answer: Option C — If a passing agreement is reached by radiotelephone, whistle signals are optional, and the vessels should pass starboard to starboard as agreed.

Per 33 CFR 83.34(h), radiotelephone agreements supersede the requirement for whistle signals. If the vessels agree to a starboard-to-starboard passage via radio, they are authorized to proceed with that maneuver without sounding the traditional whistle signals, provided the agreement is clearly understood by both parties.