Question

You (should look at a copy someday) Which letter correctly identifies the word(s) in parentheses?

Answer 1

You (should look at a copy someday). 
In this sentence, "you" is the subject, so that makes the rest the predicate. 
And it is also the entire rest of the sentence explaining what the subject should do, so it's the complete predicate.

Answer 2

Your answer is D. Complete predicate.

Look at the sentence, you cab easily find the simple subject, You, the one who is doing the action. So it can't be A.

The simple predicate is just the verb, the action (look). So it can't be B.

A complete subject is when there are words that describe the subject. Since there is no description about the subject, it can't be C.

Eventually, a complete predicate is when, besides the verb, we have when the action has begun, where it took part, how it took part etc.

Since the sentence say "look at a copy", so it says to who you should look at, it's a complete predicate.