What action makes a drop kick legal?

A drop kick becomes legal when the ball touches the ground and is then kicked. This action, characterized by the player dropping the ball directly to the ground and allowing it to bounce once before subsequently making contact with it to kick, is what defines a drop kick in football. It is important to recognize that the primary method of executing this kick allows for the ball to make contact with the ground first, which distinguishes it from other kicking methods, such as a place kick or a kick off a tee.

In contrast, a kick that occurs directly from the ground without a bounce would not meet the criteria for a drop kick as outlined in the rules, nor would a kick that occurs from a tee empower the characteristics that define a drop kick. Additionally, a kick made after the ball has already been in the air would no longer fulfill the requirement that the ball is dropped and then kicked after touching the ground. Thus, the legal definition and parameters surrounding the drop kick make option C the correct choice.