A precipitate will form when a freshly prepared aqueous carbonic acid solution is added to an aqueous solution of a. calcium hydroxide. b. sodium chloride. c. potassium carbonate. d. nitrous acid. e. ammonium chloride.

They can measure  the amount of energy gained or lost

Okay well gravitational energy is matter forced by gravity making energy though the kinetic energy then the electric energy produces electricity from the kinetic energy and the kinetic energy gets its energy from the gravitational energy. was that the answer you wanted or something else?  

Is there a picture or answer choices?

The answer is the third choice