According to Einthoven's law:: (A) 1+2=3, (B) 1+3=2, (C) 2+3=1, (D) 1+2+3=0
Answer is B. The sum of the voltages in lead 1&3 equals the voltage in lead 2, mathematically this principle is called as Einthoven law.
Einthoven’s Law:
Einthoven’s law states that if the ECGs are recorded simultaneously with the three limb leads, the sum of the potentials recorded in leads I and III will equal the potential in lead II.