Question

read the passage below and look for sentences that begin with a joining word but are missing the comma. add the missing commas to each one.
sleep is necessary to keep a persons brain and body healthy. even though a person could stay awake for longer than a week they would start feeling pretty miserable after just one sleepless day. because sleep is the only time when the brain can fully rest a lack of sleep makes it harder to do well in school, play an instrument, or even catch a football.
though adults struggle without enough sleep these effects can be more intense for children and teenagers. because their brains are still developing children need 9 to 12 hours of sleep each night. teenagers need 8 to 10 hours of sleep.
scientists have studied what happens when a person stays awake for too long. after a person stays awake for 24 hours their thinking slows down. it can also be harder to remember things. if a person hasnt slept for a full day their hand-eye coordination and reaction time also suffer. this means that its hard to succeed in sports without enough sleep.
thirty-six hours of no sleep can cause more serious problems. since the body and mind havent been able to rest it becomes nearly impossible to learn new things or be creative. a person may also start to feel sad, scared, or angry after 36 hours. their heart could even have issues after this much time awake!
after 48 hours, a person will start having microsleeps. these are tiny moments of sleep where a persons brain will force them to fall asleep for a few seconds. this can be extremely dangerous when a person is driving. while there is a lot of research about 24 - 48 hours without sleep scientists dont know much about what happens after 3 sleepless days. forcing a person to stay awake for more than 3 days is actually a form of torture, so really long studies arent allowed in many countries. even though these studies arent allowed scientists can guess that staying awake for more than 3 days would cause some serious problems for a persons body and mind.

Explanation:

When a sentence begins with a joining word (subordinating conjunction) like "Even though", "Because", "Though", "If", "Since", "While", a comma is needed after the introductory clause. This is a grammar rule for complex sentences.

Answer:

• Even though a person could stay awake for longer than a week, they would start feeling pretty miserable after just one sleepless day.
• Because sleep is the only time when the brain can fully rest, a lack of sleep makes it harder to do well in school, play an instrument, or even catch a football.
• Though adults struggle without enough sleep, these effects can be more intense for children and teenagers.
• If a person hasn't slept for a full day, their hand - eye coordination and reaction time also suffer.
• Since the body and mind haven't been able to rest, it becomes nearly impossible to learn new things or be creative.
• While there is a lot of research about 24 - 48 hours without sleep, scientists don't know much about what happens after 3 sleepless days.
• Even though these studies aren't allowed, scientists can guess that staying awake for more than 3 days would cause some serious problems for a person's body and mind.