Gene refers to the small unit of chromosome related to biological morphology; Traits refer to biological morphological characteristics, physiological characteristics and behavior patterns. Genes control biological traits. Huang et al. transferred the protein gene of American flounder into tomato to cultivate cold-resistant tomato. By changing tomato gene, the gene of American flounder was injected into tomato DNA by microinjection technology to cultivate cold-resistant tomato. This technology is called transgenic technology. It can be seen that B meets the problem.

So choose: B.