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Answer: Choice A. x^2+9</h3>
This is a sum of squares, which cannot be factored over the real numbers. You'll need to involve complex numbers to be able to factor, though its likely your teacher hasn't covered that topic yet (though I could be mistaken and your teacher has mentioned it).
Choice B can be factored through the difference of squares rule. Therefore, choice B is not prime.
Choice C and D can be factored by pulling out the GCF and then use the difference of squares rule afterward. So we can rule out C and D as well.
30 miles/ 1 gallon
30 miles per gallon
30/1
Is it necessary
Can I get it cheaper elsewhere
Will it last a while
These are just 3 I came up with. I do not know if they are what your teacher would have put.
The algebraic expressions can be written as

The given expression is,