D. CuCl2 copper(2)chloride
Answer : The excess reactant in the combustion of methane in opem atmosphere is 
molecule.
Solution : Given,
Mass of methane = 23 g
Molar mass of methane = 16.04 g/mole
The Net balanced chemical reaction for combustion of methane is,
First we have to calculate the moles of methane.
= 
= 1.434 moles
From the above chemical reaction, we conclude that
1 mole of methane react with the 2 moles of oxygen
and 1.434 moles of methane react to give 
moles of oxygen
The Moles of oxygen = 2.868 moles
Now we conclude that the moles of oxygen are more than the moles of methane.
Therefore, the excess reactant in the combustion of methane in open atmosphere is molecule.
Answer : Option A) The body breaks down the molecules into molecules they need.
Explanation : Nutrient molecules are important because the body breaks the nutrient molecules and convert it into the absorb-able molecule that can generate energy for doing the activities of the body.
Nutrients are taken in the body in the form of carbohydrates which later on gets broken into glucose molecules and generates energy, proteins which is decomposed into amino acids, fats breaks down into fatty acids, minerals and salts are also nutrients which is essential nutrient for body.
Approximately 99 because there is the same amount of electrons and the only things that go into the nucleus is protons and neutrons.
