Answer:
a. pure water
Explanation:
In liquid solutions the current is conducted by free ions present in the solution.
So here we know that all of the following condition the free ions are present in it.
1) Tap water
2) Aquarium Water
3) Ocean Water
All of them has free ions as impurity in it due to which current will flow in it while if water is in pure state then in that case the ions are not present in it to conduct the electricity
So here correct answer would be
a. pure water
