Answer:
requiring physical education in schools
Step-by-step explanation:
In order to accelerate the prevention of obesity, the federal government needs to take some initiatives. Among the choices listed above, "requiring physical education in schools" is the most doable.
This will have an early impact on children who might become obese in the future. Providing them physical exercises will increase their activity level, thereby increasing the calorie burn from eating unhealthy food. This will also curve their bad eating habit, thus leading to more healthy diet in the future.
Directly establishing farmer's markets doesn't necessarily mean that the people will buy from them, thus it becomes unclear whether this can combat obesity.
Producing advertisement for junk foods is definitely not good. This will attract more people to buy unhealthy foods.
Decreasing sales tax on food products will enable people to buy more food. They'll tend to overbuy and, in turn, overeat.