Two students were doing an experiment which involved adding potassium sulfate powder to water. They added one teaspoon of potassium sulfate to the water and stirred it, and all the powder dissolved. They continued to do this until, after the fourth teaspoon, no more potassium sulfate would dissolve. As more potassium sulfate dissolves in the water, the mixture becomes

a. more concentrated.
b. less concentrated.
c. dilute.
d. more cloudy.