Question

which property is used to identify the electric charge on the object

Answer 1

There are two types of charges . We call it as Positive charge and negative charge.

Electric charge is the property of an object that causes it to attract or repel from another charged object .
Gold leaf electroscope and Pith ball electroscope are used to detect the charge on the object.

The property on which we can find out the presence of charge on object is:
---> Like charges repel
---> unlike charges attract.
For example :To identify the charge on electroscope. First we need to charge electroscope with known charge[let us say positive charge]. The leaves will get positively charged and move apart. Then touch the disc of electroscope with other object we need to test

Answer 2

The best answer of your question is "repulsive property"
Well, the electric charge may cause the attraction as well as the repulsion between two charged bodies

Te attraction is due to opposite charges between the charged bodies but this may also due to induction attraction development between uncharged body.which means opposite charge can also induced in neutral object.  So the repulsive property or repulsion is the excellent way to identify the electric charge.
hope this helps.