What safety equipment must all personnel in the boat wear?

The correct choice is lifejackets and hardhats because these items are essential for ensuring the safety of personnel on a boat. Lifejackets provide buoyancy and prevent drowning in case someone falls overboard or is otherwise immersed in water. This is a critical safety requirement in maritime environments where the risk of water-related accidents is significant.

Hardhats are typically required to protect against head injuries, especially when working in an environment where there may be risks of falling objects or collisions. Combining the use of lifejackets and hardhats addresses both the risk of water immersion and the potential hazards present on a boat, thereby ensuring comprehensive safety for all personnel.

Other options may include gear that has specific applications but do not provide the same fundamental level of safety required in a boating environment as lifejackets and hardhats do.