I think the correct answer from the choices listed above is the second option. The enzyme pepsin that is present in the stomach denature in the intestine due to the alkaline environment of the intestine. This is because pepsin has an optimum pH that is very low which is ideal for the acidic conditions of the stomach.
Your answer here is Commensalism by process of elimination
They are both the building blocks of life
A hypotonic solution<em /> would cause the bacterial cell to lyse or burst. This happens via osmosis. When the concentration of solutes is higher inside the cell, water will move towards that higher concentration because it tries to balance things out. When a lot of water gets into the cell and it can no longer handle it anymore, it will burst or lyse.