The main nutrients needed by human body are: sugar, fat, protein, water, inorganic salts and vitamins. The rice in this dinner mainly provides sugar, while the steamed perch and Mapo tofu mainly provide protein, oil and inorganic salts. Lack of vegetables and fruits will lead to insufficient vitamin intake, so it is more reasonable to supplement some vegetables and fruits. It can be seen that option b meets the meaning of the question.

Therefore, choose: B.