An aircraft has indicated that he wants you to change §course and follow him. You cannot comply because of an §emergency on board. Which signal should you make?

A
Fire a red flare at night or a red smoke signal by day
B
Send the Morse signal "N" by flashing light
C
Make a round turn (360°) and resume course
D
Make an "S" turn (hard right then hard left) and resume course
E