There are a few key methods to calculate the rate of photosynthesis. These include:
1) Measuring the uptake of CO2
2) Measuring the production of O2
3) Measuring the production of carbohydrates
4) Measuring the increase in dry mass
As the equation for respiration is almost the reverse of the one for photosynthesis, you will need to think whether these methods measure photosynthesis alone or whether they are measuring the balance between photosynthesis and respiration.
It's answer is 3 a squirrel gathering acorns from a oak tree.
The first law of thermodynamics is equivalent to the law of conservation of energy: energy cannot be created or destroyed; the total amount of energy in the Universe is fixed. Energy can be transformed from one form to another or transferred from one place to another but the total energy must remain unchanged.
