Health education is carried out to promote people to spontaneously and consciously accept and adopt healthy behaviors and lifestyles, eradicate or reduce risk factors that affect health, prevent diseases, and achieve the goals of promoting physical and mental health and improving quality of life Organized and planned social education activities. According to the above definitions, Which of the following are health education:. ['A company holds a health knowledge lecture in the countryside and uses this as an opportunity to sell health products to old people.', 'An elective course for "mental health" offered by a college is very popular among students, and even nearby citizens come to take courses.', 'On Sunday, a hospital organized medical staff to hold a free clinic in the community square, providing residents with free blood pressure measurement, temperature measurement and medical consultation services.', 'In order to prevent the high incidence of cardiovascular and cerebrovascular diseases in the elderly since the autumn, the community hires well-known experts to hold a series of lectures for elderly residents every September to popularize relevant medical knowledge.']