Which is wall -less and smallest living cell

Which of the following is the wall-less and smallest living cell?

The smallest living cell is :

Which organism are the smallest living cells knonw and can survive without oxygen?

Which organism are the smallest living cells knonw and can survive without oxygen?

Which organism are the smallest living cells known and can survive without oxygen?

Which of the following organisms completely lack cell wall, they are the smallest living cells known and can servive without oxygen ?

Which of the following organisms completely lack cell wall, they are the smallest living cells known and can servive without oxygen ?

What is true for Mycoplasma? 1. They completely lack cell wall 2. They are the smallest living cells known 3. They can survive without oxygen 4. All the above