How did improving treatment of patients with antibiotics lead to a new problem?

The new problem that arised after antibiotics was that the disease became immune to the antibiotics. So we had to make a better antibiotics that would fight this disease that was resistant to the old antibiotics.

Some bacteria became immune to antibiotics because of over use of the antibiotics. Therefore in the future antibiotics will no longer work because bacteria will become more and more immune to the point antibiotics will no longer work

The correct answer is  b)