Phillip was performing a laboratory exercise on how temperature affects a plant's cellular activity. he discovered that when exposed to high temperatures (around 50 degrees celsius), the overall rate of glucose production by photosynthesis decreased.
which of these conclusions would best explain why this occurred?

Hello
We know that biological processes are carried out by organic catalysts known as enzymes. Enzymes are protein molecules that operate over a range of conditions, and a specific set of those conditions are ideal for them. However, in most organisms that are not adapted to withstand high temperatures, the enzymes cannot operate beyond 50 degrees Celsius. This is because their structure starts to deform due to the breakage of bonds within the molecule. The break down is cause by the energy supplied in the form of temperature. An enzyme's structure is essential for it to carry out its task and is made specifically for the molecule it is to act on, the substrate. If the structure is deformed, the enzyme cannot carry out its function. Therefore, the enzymes producing glucose denature and glucose production decreases.

That would be a working theory.