The pH of the substance which tests yellow for BTB and red for CR is acidic.
What is pH?
This is referred to the power of hydrogen of a substance and it's the degree of acidity and alkalinity of a substance.
An acidic substance will turn Bromothymol blue to yellow and CR to red which was why it was chosen as the most appropriate choice.
Read more about pH here https://brainly.com/question/22390063
