which is notevedence of a chemical reaction?

Question

A bubbling B boiling C lcold light D heat E color change F tempeture drop G smoke H explosion

Answer 1

One detail that I would add to Orange's excellent answer. Dissolving white anhydrous copper sulphate in water to give a blue solution IS a chemical reaction, since in the solution (and in blue copper sulphate) there are four waters associated with the Cu2+ ion. So actually, this does show that colour changes are evidence of chemical reaction.

Answer 2

most appropriate ans: B boiling

but sometimes D(dissolution of NH4Cl in water in spite of bein a physical change shows temp drop), E(dissolution of white anhydrous CuSO4 in water although bein a physical change turns the color to blue) mayalso not indicate a chemical rxn.

btw what's the third option???????