The author visited four countries или The author has visited four countries

Объясни тупой девочке почему Рasr Simple?

Так как действие совершено и закончено в прошлом, и не имеет видимых результатов в настоящем.

Sorry I meant The asuthor visited for countries is correct

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"The author has visited four countries" is correct because you are stating a fact.You need to use the perfect tenses when talking about a past event which continues to the time being described.