The independent variable is what researchers are observing, it is called independent because researchers do not know how it will react to the conditions it is exposed, in this case, the comedy skit after a regular night’s sleep and after a sleepless night.
Answers b and c have nothing to do with the current experiment.
Answer d could be right but sense of humour will be the final conclusion of the study. First, researchers will observe students´reactions (independent variable) which will lead to a more general conclusion; sense of humor affected by the amount of sleep.
<span>European Union is a international </span>organization<span> comprising of 28 </span>European<span> countries and governing common economic, social, and security policies.</span>
They wanted to set rules for the people, the power may be the peoples' but they needed to set "ground rules". Like owning a house, its your house but you give yourself some rules.