If the sweeper would cleaned the street in morning rather than at night, he…

Concept: A modal auxiliary such as "would", "could", or "should" is always followed by the base (bare-infinitive) form of the main verb, never the past-tense form — "would clean", not "would cleaned". Separately, a specific segment of the day introduced by "in" ("in the morning", "in the afternoon", "in the evening") takes the definite article "the"; the one fixed exception is "at night", which takes no article.

Application: The given sentence has exactly two correctable faults: "would cleaned" breaks the modal-plus-base-form rule, and "in morning" drops the required article before the time-of-day noun. (The if-clause's own "would" — expressing a habitual complaint about how the sweeper goes about the work — is left untouched: every well-formed candidate keeps it, so it is not itself at issue here.) Correcting only the two faults — without changing anything else — gives: "If the sweeper would clean the street in the morning rather than at night, he might get a better chance at cleaning the corners."

Cross-check / Contrast: Checking each candidate against the same two rules rules out the others:

• Pluralizing "street" to "streets" and pairing "night" with the article "the" introduces a new determiner mismatch that the original sentence never had.

• Dropping "than" after "rather" leaves an incomplete comparison in this specific "rather than" construction — "rather" cannot stand without its paired conjunction here.

• Swapping in a sentence about a gardener and a greenhouse abandons the sweeper sentence altogether, so it cannot be a correction of it.

Result: Only the version that fixes the modal-verb form and adds the missing article — matching the sentence derived above — is the properly corrected sentence.