The right answer is d. all of these.
ACIDITY:
The pH can allow or prevent certain molecules to pass the plasma membrane, this is the case for example in plants with auxin, what is called acid growth at auxin corresponds to the fact that in acidic pH the charges present on auxin will disappear and allow it to pass more easily in the cell since the charges and therefore the polarity of auxin prevented it from diffusing freely and asked the need for special proteins to pass the membrane, in acidic pH auxin can pass even without transport protein.
The pH will influence the number of protons available, which obviously also affects everything that requires a proton pump, or proton flux, proton gradients, as well as other proteins.
Since the protons are positive, they will at the same time participate in the polarity of the cells since the charges are supposed to be distributed on both sides of the membrane and a change in the number of charges causes depolarization or hyperpolarization of the cell.
TEMPERATURE
:
The fluidity of the plasma membrane increases with temperature because of the different melting points and phospholipids that compose it.
Indeed the membrane is composed of different phospholipids which have two carbon chains in 12C minimum. And the thermodynamic properties of each of these fatty acids depend on the membrane fluidity. The higher the temperature, the closer we get to the melting points of the lipids in question, which ultimately leads to an increase in membrane permeability and vice versa.
The longer the carbon chain of the lipid is saturated, the higher the melting point, and vice versa.
