Foundations of GMAT Verbal Drill 2.1 confusion

[GMATman13]

Hi guys I am a little confused with Drill 2.1 in the foundations of GMAT verbal book from Manhattan GMAT.

It simply states that I should circle the nouns, I got questions 3, 4, and 5 wrong as I circled what I thought were compound nouns.

Here were my selections for 3, 4 and 5:

3. primary purpose, passage, alternative explanation, well-known fact

4. recent study, additional support, particular theory, origin, fruit bat.

5. I, happy, happy, my happiness, yours

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I am thinking that for:

3. Primary purpose, the primary is an adjective and so is alternative and well known which is why they would not be nouns.

4. Recent, additional, particular are adjectives as well which are not defined as nouns

5. Here I am confused because "I" is a thing, its a person, its you, so should it not be a noun? Happy is also a state of being which is a thing, no? Also is "your's" not a thing?

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What is the difference between compound nouns and adjectives and how do you recognize the difference?

Also why in #5 are "I" and "happy" not nouns?

Thanks

[jlucero]

Compound nouns should either have both words capitalized, combined with a hyphen, or make no sense when one of the two words is removed (ie. hot dogs). For each of those examples you gave, the part you shouldn't have included was an adjective giving extra (but not essential) information.

I = pronoun
happy = adjective