Even Though Many Ballparks Practice Price Discrimination Between Adults and Children

Even though many ballparks practice price discrimination between adults and children in selling tickets, such discrimination is not applied at the concession stands because

A) children's demand for food is elastic and adults' demand for food is inelastic.
B) adults' demand for food is elastic and children's demand for food is inelastic.
C) there can be exchange of the product from children, who'd buy it at a lower price, to adults.
D) there can be exchange of the product from adults, who'd buy it at a higher price, to children.