Which of the following statements is a qualitative observation? A. The branch is three meters long. B. The substance tastes bitter. C. There are eleven students absent. D. The beaker contains four hundred milliliters of an unknown liquid.

There are two kinds of analysis: qualitative and quantitative

In quantitative we analyse the amount of something that is how much of something is present / the quantity. Ex: the length of branch of tree, number of students in class, volume of a liquid in a beaker.

In qualitative analysis we determine the kind of substance / quality of substance / nature of substance.

like: colour of a substance, odor of a substance or taste (bitter / sour / sweet etc) of a substance

So answer is : B. The substance tastes bitter