21 According to the passage, why is it hard for teenagers to challenge the assumption that the goal of life is to make money and buy products?
(A)They cannot find any other hangout place better than the mall.
(B)They have been doing a lot of shopping in the mall.
(C)They can easily get bored and need to find a place to go.
(D)They are likely to be turned into consumers by spending a lot of time in the mall.