Answer:
a. additional experiments must be performed to determine the signs of the charges
e. all three objects possess charges of the same sign.
Step-by-step explanation:
When any two objects are brought close to each other and they repel each other then it is possible that they are having the same type of charge.
Here A and B when brought into proximity repel each other and also when B & C are brought close they repel each other that means all the three objects carry similar charge.
We do not know the nature of the charge and we need to perform further experiments with a known charge or a known magnetic field to determine the nature of charges on them.