While being assisted by an icebreaker on Lake Superior, you receive a single letter code instructing you to slow your vessel. Which signal could you use to signify that you are complying with the request?

A
Three blasts of the whistle
B
The code flag "A" (Alpha) displayed from a halyard
C
Four blasts of the whistle, namely 1 short 2 long and 1 short
D
The code flag "L" (Lima) displayed from a halyard
E