Answer: 2.8
Explanation: just took the quiz
The form of heat transfer taking place in the crust of the Earth would be Convection.
Reaction of option c produces precipitate.
Rhodium on reacting with potassium phosphate produces rhodium phosphate which remain in solution due to low lattice energy for rhodium phosphate.
Niobium on reacting with lithium carbonate produces niobium carbonate and it will remain in aqueous form.
Cobalt on reacting with zinc nitrate produces cobalt nitrate. This, Co(NO3 )2 is insoluble precipitate and settles at bottom whereas zinc ion will remain in solution as follows:

Potassium ion on reacting with sodium sulfide produces potassium sulfide which remain in solution
If you cut the cube and keep all the pieces you are causing only physical change
Well if the change is reversible then it is a physical change, but if not then it is a chemical change.