According to Ohm's Law, \( V = IR \), where \( V \) is the voltage, \( I \) is the current, and \( R \) is the resistance.
If the current \( I \) is halved and the voltage \( V \) remains constant, we can rearrange Ohm's Law to find resistance:
\[ R = \frac{V}{I} \]
When the current is halved, \( I \) becomes \( \frac{1}{2}I \). Therefore, if we substitute this into the equation, we get:
\[ R = \frac{V}{\frac{1}{2}I} = \frac{2V}{I} \]
This shows that the resistance \( R \) must double to maintain the same voltage when the current is halved.
So, the correct response is:
The resistance is doubled.