technology being used to help heal people. medical procedures being used to hurt people. expensive medicines being used for many purposes. the solution to one problem causing another problem.
I gave my students this multiple choice question: Some types of medicines can be used to cure people when they are sick. Some medicines, however, may cause bad reactions to the people taking them. This difference is an example of

Only one answer is correct among these 4 choices:
- technology being used to help heal people.
- medical procedures being used to hurt people.
- expensive medicines being used for many purposes.
- the solution to one problem causing another problem.

Could you tell me which one is correct?

the solution to one problem causing another problem.