ANSWER
D. 100.0
EXPLANATION
The equivalence resistance of a circuit with resistors connected in series is the sum of the resistances of each resistor. In this case, we have two resistors with a resistance of 50.0 Ohm, so the equivalent resistance is,
[tex]R_{eq}=50.0+50.0=100.0[/tex]Hence, the equivalent resistance is 100.0 Ohm.
