Which of these statements describes a constraint imposed on scientific researchers by the antarctic treaty system? a. tourist activities are carefully controlled. b. the safety of scientists is ensured. c. some activities are banned. d. scientific knowledge is not shared.

A constraint imposed on scientific researchers by the Antarctic Treaty System is that some activities are banned. So, option C is correct.

The Antarctic Treaty System is a treaty with several related agreements. Here the environment is fully protected and research is given priority. The environmental conditions are very inhospitable for visitors. The main aim is to keep the environment protected and hence several activities are banned even for scientific research purposes such as establishing military bases and use of the weapons, disposal of radioactive waste and nuclear explosion etc. Tourist activities are controlled and safety of visitors is ensured including the scientists. Many recent research developments have taken place in the twentieth century.