When a short circuit condition occurs in a circuit, it means that there is a direct path for the current to flow with very low resistance, bypassing the normal components of the circuit. In this situation, the current in the circuit will increase substantially.

Option 1: Becomes zero - This is not correct because a short circuit actually provides a path for the current to flow, so the current will not become zero.

Option 2: Remains constant - This is not correct because a short circuit causes a significant decrease in resistance, resulting in a significant increase in the current flowing through the circuit.

Option 3: Increases substantially - This is the correct answer. As mentioned earlier, a short circuit provides a low resistance path for the current to flow, resulting in a substantial increase in the current.

Option 4: Keeps on changing randomly - This is not correct because the presence of a short circuit will cause a consistent increase in the current, rather than random changes.

To summarize, when a short circuit condition occurs, the current in the circuit will increase substantially.