Answer to Question 1
D
Answer to Question 2
It is possible to demonstrate a relationship between two variables by simply observing them. However, simple observation cannot establish the direction of the relationship. For example, you may observe that two variables change together consistently: as variable A increases, variable B also increases. However, you cannot determine whether changes in A are causing changes in B, or whether changes in B are causing changes in A. To avoid this problem in an experiment, the researcher takes charge and manipulates one of the variables. For example, the researcher increases the value of variable A and then observes variable B to see if it is affected by the increase. If B also increases, then the researcher can conclude that changing variable A has caused changes in variable B.
Rutherford's gold foil experiment demonstrating that most of the volume of an atom is empty spa
Overview of gas exchange between the environment, blood, and cells.
Ghostly experiment
Normal combustion is a smooth, controlled burning of the air–fuel mixture.
Variable and absorption costing, explaining operating-income differences.
Variable expressivity as shown in flies homozygous for the eyeless mutation in Drosophila