The circuit shows a resistor R connected in series with a battery and a resistor of resistance \({\text{10 }}\Omega \). The emf of the battery is 20 V and it has negligible internal resistance. The current in the circuit is 1.0 A.

Which of the following is the resistance of R?

A.     \({\text{1.0 }}\Omega \)

B.     \({\text{2.0 }}\Omega \)

C.     \({\text{10 }}\Omega \)

D.     \({\text{20 }}\Omega \)

C