What is preposetion?

Why do you oil bicycle chains and door hinges? Who was the first Astronomer Royal? How many meters in 31 feet? Why higher density air is better for combustion? Why do some companies have more success with ERP than others? What were Robert Bunsen's contributions? Are what scenarios does not describe an example of continuity over time? What objects suspend in water? Why is it easy to slip on a floor that is wet? How can you use the word yield in a sentence? How is a prediction used in scientific method? Category that contains one genus or more? What study design involves measuring the same participants over some period of time? What possible problems that may arise when a communicator interprets feedback from his audience? What is the purpose of the variable in an experiment? Why do you have to collect data correctly and accurately when studying science? What temperature is 30 degrees? What is -40 degrees Fahrenheit into Celsius? Who was the naturalist who taught that friction slowed down and stopped moving objects but they did not want to stay at rest? Convert 500 milliliter oz?