The ph indicator bromothymol blue is blue in an alkaline solution and yellow in an acidic solution. a slight increase in acidity, such as when co2 gas is added, causes a solution with the indicator to change from blue to yellow. a solution with the indicator would be most likely to turn from yellow to blue when which combination of factors exists? a. yeast cells and sugar are placed in the solution. b. water plants in the solution are placed under a bright lamp. c. algae are placed in the solution and left in a dark room. d. a person blows air into the solution through a straw.

The answer is B.

Explanation:

The pH indicator bromothymol blue is blue in alkaline solution and yellow in an acidic solution. A solution in which the color of the indicator is yellow is already acidic, hence, to change the color to blue would require that the pH of the solution is increased from acidic to basic.

Therefore, the only action that will likely reduce the acidity of the solution by increasing the pH and thus turn the color of the indicator from yellow to blue is the presence of water plants in the solution placed under a bright lamp.

More on pH indicators can be found here:

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