The equation for photosynthesis is:

[tex]\[ 6 H_2 O \text{ (water) } + 6 CO_2 \text{ (carbon dioxide) } + \text{Light Energy} \rightarrow C_6 H_{12} O_6 \text{ (glucose) } + 6 O_2 \text{ (oxygen)}. \][/tex]

When first discovered, scientists were trying to decide if the oxygen in the product came from carbon dioxide or water. Which statement describes how scientists traced the path of oxygen?

A. They used a radioactive isotope and tracked it with a Becquerel counter.
B. They used a radioactive isotope and tracked it with a Geiger counter.
C. They used a stable isotope and tracked it with a Becquerel counter.
D. They used a stable isotope and tracked it with a Geiger counter.