Which one of the following is the correct observation for the reaction between sodium carbonate and dilute sulphuric acid? a. Bubbles of a colourless gas
b. Colourless gas
c. No observable change
d. Bubbles of a greenish yellow gas

You would be correct, boiling water does disinfect contamination.    the property of disinfecting means to kill  germs, bacteria and other pathogens or contamination  that might cause an infection or cause a person to become sickly. a couple methods of disinfecting are using soap, other cleaning supplies or by simply "boiling" the contaminate.  the reason why boiling water disinfects certain attributes is because some cells cannot survive the heat and pressure.

Ithink about 50 % of an original isotope's number of atoms remain