Why can't researchers study REM sleep easily?

Sleep is an important part of your daily routine—you spend about one-third of your time doing it.  Quality sleep – and getting enough of it at the right times -- is as essential to survival as food and water.  Without sleep you can’t form or maintain the pathways in your brain that let you learn and create new memories, and it’s harder to concentrate and respond quickly.

Sleep is important to a number of brain functions, including how nerve cells (neurons) communicate with each other.  In fact, your brain and body stay remarkably active while you sleep.  Recent findings suggest that sleep plays a housekeeping role that removes toxins in your brain that build up while you are awake.  

Everyone needs sleep, but its biological purpose remains a mystery.  Sleep affects almost every type of tissue and system in the body – from the brain, heart, and lungs to metabolism, immune function, mood, and disease resistance.  Research shows that a chronic lack of sleep, or getting poor quality sleep, increases the risk of disorders including high blood pressure, cardiovascular disease, diabetes, depression, and obesity.

Sleep is a complex and dynamic process that affects how you function in ways scientists are now beginning to understand.  This booklet describes how your need for sleep is regulated and what happens in the brain during sleep.

Explanation:

https://www.ninds.nih.gov/Disorders/Patient-Caregiver-Education/Understanding-Sleep

the correct answer is the following.

one of the groups i belong to is the boy scouts. this is a problem-solving group because it has tasks that we need to solve in order to other people in different activities such as the rescue of lost pets, or elder people in need.

the other group i belong to is kids pro environment, and is an information-sharing group that tries to create conscience about the risks and problems that generate pollution in our cities. we share information to other students and parents on the importance of keep our communities clean and our skies clear.  

the simple predicate of the sentence is camped.