The four limitations are
1.It's often impossible to repeat trials on the same subjects.
2-Subjects may report an inaccurate medical history.
3-It can be difficult to control all possible variables.
4-It's impossible to come up with testable scientific questions for human subjects.
Research involving human beings is ultimately necessary for improvements in human health and welfare. Any results about healthy physiology, illness causes, treatment effectiveness, learning, or behavior must be verified by carefully controlled investigations involving human participants. Sadly, not all human research have been valid and beneficial. It is possible to harm people in the name of research. The most well-known instances happened in Nazi Germany. Investigations conducted after the war found several crimes, including experiments in which participants were submerged in extremely cold water to determine how long it would take them to pass away from hypothermia.
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Humans benefit from the domestic dog because they reduce stress, they can prevent depression, and they can improve your health. Dogs benefit from humans because they love the bond they have with their owner.
Answer:
The correct answer is A. The larynx moves up against epiglottis when food is swallowed to prevent passage of food into it.
Explanation:
The epiglottis is a moist, cartilaginous structure that is part of the cartilaginous skeleton of the larynx. It also marks the boundary between the oropharynx and the laryngopharynx. The epiglottis obstructs the passage of the bolus at the time of swallowing preventing it from going to the respiratory system.
Larynx closure occurs when the vestibular and vocal folds approach the midline during swallowing. Occasionally, when you eat very fast, solid foods or liquids can enter the larynx.