Final answer:
The voltage across a resistance in a loop circuit can be calculated using Ohm's law. In this case, the voltage across the resistance is c) 2R1.
Step-by-step explanation:
The voltage across a resistance in a loop circuit can be calculated using Ohm's law, which states that V = IR, where V is the voltage, I is the current, and R is the resistance. In this case, the current is given as 2A and the resistance is R1. Therefore, the voltage across the resistance is 2A * R1 = 2R1.
So the correct answer is c) 2R1.