Question

fix any words that are used incorrectly. if there are no errors, submit the text without making any changes.

extremely bright lightning flashes known as sprites occur in earths upper atmosphere, but scientists believe that they may effect low-level cloud cover.

Explanation:

The word "effect" is incorrectly used here. "Effect" is most commonly a noun, while the sentence requires a verb meaning "to bring about a change". The correct verb form is "affect".

Answer:

Extremely bright lightning flashes known as sprites occur in Earth's upper atmosphere, but scientists believe that they may affect low-level cloud cover.