A．pigs, cows and mosquitoes that have gone through the transgenic procedure
B．pigs, cows, sheep and chickens that have accepted additional genes
C．leaner pigs, poultry that produce pharmaceuticals and healthier sheep
D．leaner pigs, chickens resisting diseases and goats that produce milk with medicine in it

A．After injection, the embryo gets a copy of the new gene as it divides.
B．The injection method is less good because the new gene sometimes fails to join the embryo's genes.
C．The retrovirus multiplies after it enters the cell.
D．The incorporating method is less simple but better.