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.
Leder's experiment showing the binding of mRNA to DNA that contains an intron
The standard protocol of a metagenomics experiment.
The swan neck flask experiment
A Schematic Description of the Experiment by Maviel et al. (2004)
The transfer experiment that demonstrated the existence of RNA primers in DNA replication
Economic activity as viewed by environment and ecological economists