The temperature at which a fluid membrane becomes a rigid crystal is called the phase transition temperature. If one bilayer has a higher degree of fluidity than a second bilayer, the phase transition temperature of the first bilayer is:

Higher

Explanation:

The phase transition temperature is the temperature at which the membrane of cell membrane becomes rigid and attain a crystal structure.

The phase transition temperature is affected by the fluidity of the membrane that is degree of fluidity is directly proportional to the phase transition temperature.

In the given question, if one layer has high fluidity therefore the phase transition temperature of that layer will be higher.

Thus, higher is correct answer.