Choose the correct alternative which will improve the quoted part of the given…

Concept: Sentence-correction items test two things at once: which grammatical form the context requires (the possessive adjective 'your', not the contraction 'you're', immediately before a noun) and which form the sentence's own existing wording already has right (a noun's number, given in the original quoted phrase). A correct replacement fixes only the actual error present, without altering anything the original phrase already had right.

Application: In the quoted phrase 'keep you're eye', the word 'you're' (a contraction of 'you are') is used directly before the noun 'eye', a position that grammatically calls for the possessive adjective 'your' ('belonging to you'), not the contraction. The noun 'eye' itself is already singular in the original phrase, matching the idiom that pairs this verb with a singular noun. So the one genuine error here is the contraction, and the correction should replace only that, leaving the noun's number untouched.

Contrast:

• 'Keep you're eyes' — still carries the same contraction/possessive error as the original, and additionally alters the noun's number, layering a second change onto the uncorrected first one.

• 'Keep your eyes' — corrects the contraction but also changes the noun's number, an alteration the original quoted phrase never called for.

• 'No error' — incorrect, since the contraction is grammatically wrong in this possessive position.

Result: The alternative that fixes only the genuine error — replacing the contraction with the possessive adjective while leaving the noun exactly as given — is 'Keep your eye'.