A group of rats placed in an air-tight box for some hours died because they
- breathed in air containing nitrogen.
- produced carbon dioxide
- ran short of energy
-
used up the available oxygen
The correct answer is: D
Explanation
Rats, like all mammals, require oxygen to survive. They breathe in oxygen and breathe out carbon dioxide, a process known as respiration. In an air-tight box, the available oxygen would eventually be used up, and the rats would die from lack of oxygen, not from the presence of carbon dioxide or nitrogen, or from running out of energy.