The correct sentence is:
"The bike on the bike rack is blue."
The other sentences contain grammatical errors. Here’s a quick breakdown:
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"The surface of the parking lots were redone this summer." - Should be "was" instead of "were" because "surface" is singular.
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"The cars in the parking lot belongs to the teachers." - Should be "belong" instead of "belongs" because "cars" is plural.
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"The sidewalks in the courtyards has been decorated with chalk." - Should be "have" instead of "has" because "sidewalks" is plural.