Oxygen-16 is the right answer as this isotope is not used in any type of radioactive dating, instead the oxygen isotopes are used for determening the processes in the living organisms.
Carbon-14 is not correct because it is one of the most commonly used isotopes for radioactive dating, being the most precise to a certain point of age.
Uranium-235 is not correct because it is an isotope commonly used for rafdioactive dating, especially for much longer periods.
Potassium-40 is not correct because in combination with argon-40 it is one of the main isotopes for determening the age through radioactive dating.
"Nasser's decision threatened British and French stock holdings in the Company and, as the Canal afforded Western countries access to Middle Eastern oil, also threatened to cut off Europe's oil supply." according to an article.
