Astudent wants to answer the question “does adding calcium powder to soil make pea plants grow faster? ” she adds calcium powder to the soil of 12 plants and does not add it to the soil of a second group of 12 plants. she measures the growth of all of the plants in each group for a month. which statement best summarizes the factors that need to be controlled in this experiment?

Choose the best explanation of the difference between evolution and natural selection. a. natural selection is the idea that species change over time, and evolution is the idea that our world changes over time. b. evolution is the idea that species change over time, and natural selection is the idea that nature changes over time. c. natural selection is the idea that species change over time, and evolution is the idea that the species' food source also changes over time. d. evolution is the idea that species change over time, and natural selection is a mechanism by which evolution takes place.