After deciding what the variables of an experiment are, a scientist should write out a , which is a step-by-step list of directions for performng the experiment, including the instruments to be used and how to use them. A) procedure
B) hypothesis
C) conclusion

Layer r contains a well-known index fossil that is 100 million years old. based on this information and the principle of superposition, a. layers t and m are older than 100 million years, and layers x and g are younger than 100 million years. b. layers t, m, x, and g are all older than 100 million years. c. layers t and m are younger than 100 million years, and layers x and g are older than 100 million years.