In the given situation, which one of the instructions is correct?Having pressed the blue button, you have to enter the code, and then press the red button.

A、Press the blue and red buttons and enter the code;
B、Enter the code, then press the red button, and finally press the blue button;
C、Press the blue button, then enter the code. Finally, press the red button;
D、Press the red button, then enter the code. Finally, press the blue button