Which option correctly describes the different types of immunity?
- Anatural active: antibodies cross the placenta; natural passive: injection of antigens; artificial active: injection of antibodies; artificial passive: no memory cells form
- Bnatural active: memory cells form; natural passive: antibodies cross the placenta; artificial active: injection of antigens; artificial passive: injection of antibodies
- Cnatural active: injection of antibodies; natural passive: memory cells form; artificial active: antibodies cross the placenta; artificial passive: injection of antigens
- Dnatural active: injection of antigens; natural passive: injection of antibodies; artificial active: no memory cells form; artificial passive: antibodies cross the placenta