This seems to be confusing. If a risk of collision has already been deemed to exist then the only response should be to take avoiding action immediately. Thus, D would be the correct answer.
Though understanding that time does exist at a distance of 1.5nm, you would provide time for the give-way vessel to maneuver. Allowing for C to be correct. Yet, that is not what is stated by "believing that risk of collision exists."
Though understanding that time does exist at a distance of 1.5nm, you would provide time for the give-way vessel to maneuver. Allowing for C to be correct. Yet, that is not what is stated by "believing that risk of collision exists."