Read section 2 of that document. That tell you what an RTOS has to have.
Section 3 tells you why Unix fails. Section 4 tells you some things you can do to Unix to make it better.
Section 5 (specifically 5.2) tells you why windows fails. Section 5.3 compares Linus to Windows (to contrast their failures).
Section 6 deals with POSIX which isn't an operating system, it's an interface convention.
Section 7 tells you about some real RTOS's. Three I'm familiar with are QNX, VxWorks, and WinCE. Both are listed.
I really do advise that you read the materials that are given to you because they actually contain useful information and will allow you to answer the questions. There is an activity called "Study" that involves you reading material given to you. I can highly recommend it. If you're having trouble understanding that material, then ask us questions about the study material, not the questions.
If you look at the summary on page 28 of that document you'll find a list of things that you should be conversant with after reading the material. If you're not, you've missed major stuff and you should review it again.
Some of the exercises at the end relate to the material in this document, others seem to extend beyond it (but I've not studied the document in any detail). OK, I looked at one that I was doubtful about and it's answered in this document. So after studying the document you should be able to either answer these from memory or look them up.
Asking us for answers is no shortcut to actual knowledge, you have to reach an understanding yourself.