A, the picture shows the process of cultivating carrot tissue into a complete plant, so A is correct;

B, plant tissue culture requires aseptic and non-toxic conditions, so the culture process needs to be sterilized and carried out under aseptic conditions, so B is correct;

C, when the ratio of cytokinin to auxin is high, promoting the germination of callus; When the ratio of cytokinin to auxin is low, it promotes the rooting of callus; When the bud roots grow out, the ratio of cytokinin to auxin is equal, which promotes the growth of seedlings. Therefore, the ratio of cytokinin to auxin concentration in A, B and C is different, so C is wrong.

D. according to option c, the concentration ratios of cytokinin and auxin in a, b and c are different, so d is correct.

So choose C.