The simulation shows a uniform electric field. Does Case 1 or Case 2 show a test charge?

1. Only Case 1
2. Only Case 2
3. Both cases show a test charge
4. Neither case shows a test charge

A test charge has a small enough charge that it has a negligible impact on the electric field. That is true only with case 1.

In the "Two Charges" situation use the positive test charge to determine the signs of the two charges.

1. Both charges are positive
2. Both charges are negative
3. Charge 1 is positive and Charge 2 is negative
4. Charge 2 is negative and Charge 2 is positive
5. There is not enough information given to decide

Both charges are negative.