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Need a little help with ER diagram

Hi everyone and thanks for having me. This is my first time on an SQL forum. I began learning SQL recently since I want to expand my IT knowledge and skill. I am currently watching Youtube tutorials but also relying on some books I've got a hold of to cover more ground. I am currently learning ER diagrams and while I understand the basic principles, as well as commands, I have stumbled upon two examples from a book, which I can't wrap my head around. I've reconstructed them from a book I've got and there's no explanation what the error might be, even if there is one at all. I was hoping some of you can help me and explain to me what's wrong with these two. Thank you very much in advance.
(Edited to change one typo in the text on image)

Not a lot of info to go on.

But, for one thing, the "test" entity should be a stand-alone entity without any student_id assigned to it. A test exists before anyone takes it (and can continue to exist even if you decide never to give it to anyone).

There will be a separate test & student entity that will provide info on when (the date/datetime) a student took a test, their score, etc..

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