Question

Есть ли среди этих предложений Present simple?

His achievements since his accident have shown him to be a real-life superman.

They've already proved that it's possible for nerves in the spinal cords of animals to regrow and reconnect.

At first, he couldn't breathe without a machine, but now he can breathe on his own.

Answer 1

... it's possible for nerves in the spinal cords of animals to regrow and reconnect.
... but now he can breathe on his own.
в этих частях ваших предложений - Present Simple.