Answer:
C. 80V
Step-by-step explanation:
Method 1: The total resistance is 100+25=125. The 100 takes 4/5 of the voltage drop, 4/5 of 100V = 80V
Method 2: The current I through the circuit is I = V/R = 100 / 125 = 0.8A
The voltage drop of 100Ω when 0.8A flows through it is V=I*R = 0.8 * 100 = 80V