The correct option is A.
In the living cells, the only type of energy that the cells can use for their life sustaining activities is ATP [Adenosine Tri Phosphate]. ATP molecules are usually formed during the process of cellular respiration. ADP [Adenosine Tri Phosphate] is a low energy molecule in the living cells, which can easily be converted to ATP, this is done by combing a single molecule of phosphate to ADP in order to produce ATP. Thus, ADP + P + Energy = ATP.
ADP + P + energy were combined in a cell to convert a lower-energy molecule into a higher-energy molecule
answers: to make sure that all of the broken pieces of tablet were added to the water, to allow for fair comparison of all three trials, with different particle sizes to avoid experimental error