Final answer:
A golfer's stroke at a ball that falls off the tee during the stroke is considered valid. The stroke counts and the player continues from where the ball lies.
Step-by-step explanation:
If a golfer makes a stroke at a ball while it is falling or after it has fallen off the tee, the stroke is considered valid according to the rules of golf. The player simply counts the stroke and plays the ball from where it lies if it was accidentally knocked off the tee in making a stroke. However, if the ball falls off the tee when the golfer is not making a stroke or due to natural forces like the wind, the golfer can re-tee the ball without penalty. In the case where a stroke was made, it would count as one stroke and the golfer would continue play with the ball in its new position.