How are blue and red litmus papers alike? They both change color in acids.
They both change color in bases.
They both turn purple in neutrals.

3.

Explanation:

Both red and blue litmus papers are changing color in acid and the main use of them is to test whether a solution is basic or acidic.

Under acidic conditions, blue litmus paper will turn red, and red litmus paper will turn blue under basic conditions.

Purple litmus paper is always neutral which means that blue and red will always be purple in neutral environment.

the answer is true when observing or determining population size, a direct observation is use, in which each organism is counted in a population or in an area. one benefit of this measure is that you get the exact population count but it will take a long time to  determine  the  size  of a  population.