In several of the experiments we have learnt that fire needs oxygen to burn

Can you repeat this sentence, but add in punctuation?
In several of the experiments, we have learnt that fire needs oxygen to burn.
This checkin deadline will remain the same even if the departure of the flight is delayed

Can you repeat this sentence, but add in punctuation?
This check-in deadline will remain the same even if the departure of the flight is delayed.
A person with a low level of P450 enzymes will have a much lower ability to detoxify consumed and inhaled chemicals than people with a high level of P450 enzymes

Can you repeat this sentence, but add in punctuation?
A person with a low level of P450 enzymes will have a much lower ability to detoxify consumed and inhaled chemicals than people with a high level of P450 enzymes.