Question

read this example of incorrect sentence structure.
heavy, black clouds rushing in from the horizon.
which revision corrects the sentence?
heavy, black clouds rushing in from the horizon, get under cover.
heavy, black clouds rushing in from the horizon. its about to rain.
heavy, black clouds rushing in from the horizon when its about to rain.
heavy, black clouds rushing in from the horizon mean a storm is coming.

Explanation:

The original sentence "Heavy, black clouds rushing in from the horizon" is a fragment. A complete sentence should have a subject and a predicate. The option "Heavy, black clouds rushing in from the horizon. It's about to rain." adds a complete thought (the predicate part "It's about to rain") to make it a proper sentence structure. The other options either still have issues (like "Heavy, black clouds rushing in from the horizon, get under cover." which has a comma splice if we consider the two parts as independent clauses without proper conjunction) or are not as grammatically correct in forming a complete sentence structure as the option with "It's about to rain".

Answer:

Heavy, black clouds rushing in from the horizon. It's about to rain.