Choose the Odd One Out:
1. Human heart, Fish heart, Reptile heart, Toad heart.
2. Artery, Vein, Portal vein, Lacteal.
3. RBC, ATP, WBC, Platelets.
4. Purkinje fibres, A. V. node, A. V. valve, S. A. node.
5. Mitral valve, Tricuspid valve, Semilunar valve, Venous valve.
6. Systolic pressure, Diastolic pressure, Stethoscope, Sphygmomanometer.