Which percentage is in the appropriate range for a snack to be considered a "good source" of nutrients? 15% 35% 40% 50%

A percentage which is considered a good range for a snack to be considered a good source of nutrients would be 15%. The reason for this is that we should really limit our intake of snacks because these are often rather unhealthy. For that reason, it is better when snacks represent a smaller amount of nutrient intake. 

Edit your question hun so we know the choices

This is true. yes. indeed.