Which sentence has the correct subject-verb agreement?
lightning bolts flash across the sky.
lightning bolts flashes across the sky.

The correct answer is A. Lightning bolts flash across the sky

Explanation:

In grammar, the term subject-verb agreement refers to the concordance that should exist between the number of the subject and the number in the verb, this basically means that if the subject in a sentence is plural the verb should equally be plural and if the subject is singular the verb should be singular, otherwise the sentence would be grammatically incorrect. Additionally, for determining whether there is a correct subject-verb agreement it is necessary to identify whether the subject is plural or singular and whether the verb form is plural or singular. In the case presented, the subject which is the agent of the action is "Lighting bolts" which is a plural noun as it ends in "s" and expresses more than one unit, this means the verb should be equally plural and therefore the correct verb form in this case is "flash" instead of "flashes" which is used for singular nouns such as she, he or it. Thus, the correct subject-verb agreement is "Lightning bolts flash across the sky" as in this sentence both the subject and the verb are plural.