According to NFPA 1403, the person responsible for planning and coordinating all training activities is the:

The correct answer identifies the instructor in charge as the individual responsible for planning and coordinating all training activities in accordance with NFPA 1403. This role is crucial as it encompasses the overall oversight of the training program, ensuring that it meets safety standards, adheres to protocols, and aligns with the objectives of the training.

The instructor in charge is tasked with creating a structured training environment that emphasizes safety and effective learning for all participants. This includes coordinating with other instructors, preparing necessary materials, and ensuring that the training meets established guidelines and regulations. The emphasis on this role aligns with NFPA 1403's goal of fostering a safe and structured training experience.

In contrast, the other roles mentioned—incident commander, safety officer, and lead instructor—can have important responsibilities within a training context, such as overseeing operations during a live drill or monitoring safety protocols. However, they do not encompass the comprehensive planning and coordination responsibilities specified for the instructor in charge under NFPA 1403.