Researchers developed a new approach to explore whether knee cartilage repairs itself by measuring the carbon-14 in patients' knee cartilage molecules. Carbon-14 is an isotope whose prevalence in currently in the atmosphere but reflected the amount frels, then researchers could conclude that the cartilage was formed more recently. Conversely, if the carbon-14 levels did not match those approach allowed the researchers to demonstrate that mom an earlier time, researchers could conclude the cartilage was older, reflecting the carbon-14 in the atmosphere when it was made. This
Which of the following can be inferred from this paragraph?
a. Carbon-14 is a dangerous substance, demonstrated by its ability to infiltrate developing tissues in the human body.
b. Replacing knee cartilage is a very time-consuming and painful process.
c. Researchers had no way to evaluate whether knee cartilage regenerates without measuring carbon-14 in the molecules.
d. The amount of carbon-14 in molecules varies with the amount of carbon-14 in the environment when the molecule was formed.
e. Above-ground nuclear testing was banned after 1963 due to the harmful effects of carbon-14 in the environment.