Sorry but NaCl is a ionic compound not an element though it's made up of two elements sodium and chlorine
<span> Speicific heat of water is 4.2j/gm*C </span>
<span>Thus 4.2 Joules of energy is required to heat 1 gm water to 1*C. </span>
<span>or 4.2 x 30 Joules enery is required to heat 1x30 gm water by 1*C </span>
<span>or 4.2 x 30 x 80 Joules enery is required to heat 1 x 30 gm water by (100-20)*C( or required to be removed from water to cool it) </span>
Each chemical element is made up of one kind of atom, so the answer is A
