The last choice, "Teens who sleep less than 5 hours a night suffer from more immune related illnesses according to a study released in 2015 by the American Journal of Medicine." It gives a source to where the information had been gathered.
On average 30 mins but… if you mean the ENTIRE show 4 hours for sure
C. Carson’s book discusses DDT and pesticides in more technical detail than other scientific texts.
1. Study at school, if you don’t you won’t get a good job
2. In a grammar book, I suggest you should look if you have any problems