Final answer:
Lena's reliable method for helping a child who is choking on his food is safety training classes for babysitting.
Step-by-step explanation:
In the given scenario, Lena's reliable method for helping a child who is choking on his food would be safety training classes for babysitting. These classes typically cover first aid techniques, including how to respond to choking emergencies. By receiving formal training, Lena would have learned the correct procedure to handle such situations and provide immediate assistance to prevent further harm to the child. It is important to note that relying solely on personal instinct, talking with a parent, or years of watching younger siblings may not equip Lena with the necessary skills and knowledge required to effectively respond to a choking incident.
Learn more about Choking first aid