Which of the following should be included in a diver's pre-dive checklist?

Including oxygen tank pressure in a diver's pre-dive checklist is essential for ensuring safety and preparedness before a dive. This check verifies that the diver has an adequate amount of air for the planned dive duration and depth, which is critical for preventing situations of running low on air underwater. Recognizing the pressure level in the tank allows divers to assess whether they have sufficient gas to complete their dive safely and ascend while adhering to safety protocols.

Monitoring factors like water temperature, carbon monoxide levels, and the time of sunset can be part of safety considerations, but they do not directly impact the diver's immediate ability to breathe underwater during the dive. Water temperature can influence comfort and exposure protection needs, and checking air quality and environmental conditions is important but secondary to ensuring that the diver's air supply is secure. Likewise, while knowing the time of sunset is important for planning to surface before dark, it does not have a direct effect on dive execution as oxygen tank pressure does.