. absorbance readings of four prepared tubes with various solutions over a 6060-minute period. question which of the following best justifies the use of tube 22 as a control treatment? responses it was a negative control for the accuracy of the spectrophotometer, ensuring that an accurate reading for treatment cuvette 22 would be made. it was a negative control for the accuracy of the spectrophotometer, ensuring that an accurate reading for treatment cuvette 2 would be made. it was a negative control for the chemical stability of the chlorophyll suspension, ensuring that changes in absorbance could only be attributed to changes in chlorophyll content. it was a negative control for the chemical stability of the chlorophyll suspension, ensuring that changes in absorbance could only be attributed to changes in chlorophyll content. it was a positive control for the change in dcpipdcpip color associated with changes in light intensity. it was a positive control for the change in d c p i p color associated with changes in light intensity. it was a positive control for measuring the effect of dcmudcmu on the reaction.