The correct answer is A) Extend arm with the thumb pointing up, and flex the fingers in and out for as long as the load movement is desired. This hand signal is the standard way to instruct a crane operator to raise the boom and lower the load, as per the regulations and best practices for crane operations. The extended arm with the thumb up provides a clear visual cue, and the flexing fingers indicate the continuous motion required to raise the boom and lower the load. The other options are incorrect because they do not match the standard hand signals for this specific crane operation. Option B is for a different signal, option C is for a different motion, and option D is not a recognized crane operation hand signal.