Question

A specific mutation in a certain animal leads to abnormal development of the heart and kidney, resulting in miscarriage. Why did this happen?

Nature always kills the organisms with highly lethal mutations and selects the ones with mutations which are not lethal.

Nature kills the weaker organisms and selects only the strongest organisms, which can survive and flourish.

Nature selects only the organisms with functional organ systems and kills every organism with even a minute abnormality.