Plants use sunlight to convert nutrients into energy. what form of energy transfer is taking place?

The answer is solar energy
Since plants use the solar energy captured by the chlorophyll and converts that solar energy into chemical energy (nutrients).

It should be cryosphere and hydrosphere

The answer to this will be from your lab notes/procedure. it would be best to ask another student who participated in the lab as we do not know what was done, what enzyme or if the temperature is celsius or fahrenheit. if i were to guess though i'd say the rate stopped due to enzyme denturing at high temperature