Final answer:
The procedure of initially breaking the topmost portion of a window and then working downwards is not recommended for firefighters when gaining entry into a building.
Step-by-step explanation:
The recommended procedure that would not be recommended for firefighters when breaking windows to gain entry into a building is to initially break the topmost portion of a window and then work their way to the bottom of the pane (option D).
Breaking windows from the top can cause an inward flow of oxygen, which may result in the fire growing stronger and spreading more rapidly. Instead, firefighters should aim to break the bottom portion of the window to allow for smoke and heat to escape, while minimizing the inflow of oxygen.
Additionally, firefighters should never use their hands (option C) to break glass, as this can lead to serious injuries. They should use appropriate tools, such as a glass breaker or an axe, for safety and efficiency.