According to the results of the Human Genome Project, there are about 30,000 genes on the chromosomes of human cells. Which of the following descriptions of these genes is wrong?
选项：

A:Only A small number of genes are actively expressed in each differentiated cell.;
B:Different types of genes are expressed in different cells, and the expression intensity varies with time and physiological state of the cell.;
C:As cells differentiate in different directions, different cells gradually choose to retain only a small portion of genes related to their functions.;
D:AWith the development of the embryo, some genes are gradually turned on, and some genes are gradually turned off.