The question as given is missing the initial portion of the question. I will provide the missing information below and have attached an image corresponding to the reaction vessels.
This reaction is regarding rates of reaction. The rate of a reaction depends on the ability of the molecules to collide and come into contact with each other, therefore, the smaller the vessel, the faster these collisions and thus reactions take place. The rate also depends on the temperature, where an increase in temperature generally increases the rate of reaction.
The vessels to choose from are provided in the attached image. The vessels with the lowest volume and highest temperatures will have the highest rate of reaction.
Therefore, vessel D will have the highest rate, as it has both the lowest volume of 2 L and highest temperature of 52 degrees.
Vessels A and C have the next lowest volume of 3 L, but one takes place at 51 degrees and the other at 52. Therefore, with constant volume, the vessel with the higher temperature will react faster. Vessel C will have the second highest rate, followed by vessel A.
That leaves us with vessel B to react the slowest, which makes sense as it has a temperature of 51 degrees but also the highest volume of 5 L.
The order of initial reaction in decreasing order is as follows:
D > C > A > B