How can you tell that a chemical habge has occurred. plz

That is choice A.

The products are different from the reactants.

This may be easy to see - for example when one of the products is precipitated, like when you add BaCL2 to Na2SO4.  The BaSO4 formed is insoluble in water and appears as a white precipitate.

each chemical family is represented as a group or column on the periodic table. based on chemical properties, there are 6 types of chemical families. group 1 represents alkali metals, group 2 represents alkaline earth metals, groups 3 to 12 represent transition metals, groups 13 to 16 represent non-metals and other metals, group 17 represents halogens and group 18 represents noble gases.