Which sentence has the correct subject-verb agreement?
heavy rains or fast-melting snow causes floods in many parts of the world.
heavy rains or fast-melting snow cause floods in many parts of the world.

A). Heavy rains or fast-melting snow causes floods in many parts of the world.

Explanation:

Subject-verb agreement is demonstrated as the grammatical rule which implies the agreement of subject and verb in terms of number. It implies that a singular noun must correspond to a singular verb while a plural must correspond to a plural verb.

As per the question, option A implies a correct subject-verb agreement as it includes the subjects 'Heavy rains' and 'fast-melting snow' are linked by coordinating conjunction 'or' that turns it singular and therefore, the verb must also be 'singular'(causes). Thus, option A is the correct answer as in option B the subject and verb do not agree in number.

the correct answer would be d.