Why couldn't you substitute 3m h2so4 for concentrated hno3 when oxidizing copper?

This question seems to be an essay question from experiment. Different solution of oxidizing agent will have different strength.  Sulfuric acid or H2SO4 is weaker oxidizing agent when compared to nitric acid (HNO3). In this case, if you subtitute the H2SO4 you wouldn't be able to get the same result for the experiment.

the correct option is c.

isotopes refers to different forms of the same element with the same atomic number but different mass number as a result of difference in their neutron numbers. isotopes have different relative atomic mass but share the same chemical properties.