The answer is a Nucleus. Eukaryotic cells have nuclei while;e prokaryotic cells do not.
Answer: The balanced chemical equation for the combustion of benzene is:

Explanation:
Combustion reactions : It is defined as the reactions in which a hydrocarbon reacts with oxygen gas to produce carbon dioxide and water as a product.
Balanced chemical reaction : It is defined as the reaction in which the number of atoms of individual elements present on reactant side must be equal to the product side.
The balanced chemical equation for the combustion of benzene will be:

By Stoichiometry of the reaction we can say that,
2 mole of benzene reacts with 15 moles of oxygen gas to produce 12 moles of carbon dioxide and 6 moles of water molecule.
Answer: The ratio of the number of oxygen molecules to the number of nitrogen molecules in these flasks is 1: 1
Explanation:
According to avogadro's law, equal volumes of all gases at same temperature and pressure have equal number of moles.
According to avogadro's law, 1 mole of every substance contains avogadro's number
of particles.
Thus as oxygen and nitrogen are at same temperature and pressure and are in equal volume flasks , they have same number of moles and thus have same number of molecules.
The ratio of the number of oxygen molecules to the number of nitrogen molecules in these flasks is 1: 1