How was it possible for Adam & Eve to be perfect what if they got bit by a poisonous snake?

They WERE perfect like immortal until Eve partook of the fruit from the Tree Of Knowledge. Then she handed it to Adam. Because they disobeyed God by taking from that tree he cast them out of the Garden of Eden. So the Garden was like the barrier of immortality because they were sinless. So when they went out to the real world, they no longer had that seal of protection because they knew right from wrong and all the things that come with it. ual contact, cleanliness, illness and so on... So if they were out of the Garden, YES they were under the threat of death as we are every second. But within the garden they were immortal. They had no worries or knew no other emotion but joy and happiness.