Which of the Following Statements Is Incorrect

Which of the following statements is incorrect?

A) Isotope dilution is a technique used to determine the quantity of a substance in a mixture by adding a known amount of an isotope to it.
B) Isotope dilution was used to elucidate the biological pathways of photosynthesis.
C) Isotope dilution may be used to determine the amount of vitamin B₁₂ in food.
D) A radioactive tracer is a very small amount of a radioactive isotope added to a system used to study the chemical,physical,or biological processes of a system.
E) Neutron activation analysis is an analysis of elements in a sample based on the conversion of stable isotopes to radioactive isotopes by bombarding a sample with neutrons.