If by positive, you mean the addition of something, choice C (Increase the intake of organic sugar and fiber) is the best answer. The other choices are negative, since they all call for the removal or limitation of something. With this, one will not loose weight if one increases the amount of sugar and fiber they consume to an extreme. If by "positive" you simply meant good, B (Limit the intake of sugars and fats) is the most probable answer. However, again, the limitation is undefined, slight limitation will have no effect on weight gain if the limited substances are replaced by different substances containing the same, or more, amount of energy. Weight gain results from unused energy (calories) which the body stores (put simply, fats and sugars store more easily, but this is a different matter). I hope I answered your question. You must find out what "positive" is supposed to mean here before you can properly answer this question.
What healthy, positive action can people take to reduce their weight gain? Remove all sugar and fat from diet Limit intake of sugars and fats Increase intake of organic sugar and fiber Decrease sugar and fiber