Reaction:

Magnesium is a stronger reducing agent than copper and is thus able to reduce copper(II) oxide.
Products of the reaction: Magnesium oxide and metallic copper.
Answer:
Carbon is the basic compound for making of molecules in biological systems. IN growth medium, carbon sources are added to provide energy.
Explanation:
Without carbon, there would be no life on earth. Carbon molecules have the ability to form bonds that are stable with a vast number of molecules. It can also form bonds with itself. The proteins, amino acids, DNA, RNA, lipids all contain carbon molecules. Hence, it serves as the basic compound for making molecules of life. In the growth culture media, Carbon is added in the form of carbohydrates like glucose or glutamine as it provides main source of energy.
C. If the mass or length of substance changes it's extensive
3/8 NA = 3/8 x 6.023 x 10^23 molecules of h2o
so, we can easily conclude that 1mole of CH4 gives 2mole of H2o