When antibiotics were first developed, most infectious diseases could be controlled by them. today certain bacteria are resistant to many antibiotics. one possible explanation for this change is what?

a few bacteria had a mutation that allowed them to resist the antibiotics, and now most of the bacteria have this mutation.

Explanation:

the last statement is correct i.e.

when your heart is not pumping enough blood around your body because your heart is severely failing, you may need an artificial heart. an artificial heart is a mechanical device, about the size of an orange, that is connected to your heart or implanted in your chest to or replace a failing heart.