Martin had many little tricks highly entertaining to his son. On an evening from the marks, he would buy a paper mask, the head of a hissing dragon. He would put it on and knock at the door. On opening the door, the boy would be terrified for a moment, but only for a moment, for he would soon remove it and the two would roll with laughter. Tom would, then go out with the mask and knock at the door for his father to open. Martin had to act as if he was paralysed with fear.
The father and son rolled with laughter after the

Options

A. father put on the mask
B. opening of the door
C. son saw the mask
D. father removed the mask