Six nutrients needed by human body: protein, sugar, oil, vitamins, inorganic salts and water; Combined with the meaning of the question, rice is rich in starch and belongs to sugar; Braised pork and spicy tofu contain oil, protein and inorganic salts, indicating that the vitamin content in food is less; Therefore, in order to make the nutritional collocation more reasonable, it is necessary to supplement foods rich in vitamins.

A, fried vegetables are rich in vitamins, so the choice is correct.

B, milk is rich in protein, so the choice is wrong.

C Steamed crucian carp is rich in protein. Wrong option.

D scrambled eggs are rich in protein, so the choice is wrong.

So choose a.