What is the correct action if the timer sounds a warning horn just before a time-out ends and A-6 reports to enter the game?

When the timer sounds a warning horn just before a time-out ends, it indicates that the time-out is about to conclude. In this situation, player A-6 must wait for the official to signal the end of the time-out before he is allowed to enter the game. Therefore, the correct action is to deny A-6's entry at that moment.

The rationale behind this rule is to ensure that player substitutions occur in an orderly manner, adhering to the time constraints set by the game. Allowing A-6 to enter while the time-out is still technically in effect could lead to confusion during the transition back to play, impacting game flow and the timing of the match. Thus, the official must not permit A-6's entry until it is appropriate to do so, which is when the time-out officially concludes and play is ready to resume.