UPSC CDS English Sentence Improvement Part 2 Questions

In the context of the given sentence, the present perfect tense should be used as the sentence conveys that the mentioned person, that is, 'I' is connected to Mr. J. Mathews since 1970 and this tense is used for something that started in the past but continues in the present. Hence, in this context, the most appropriate option is 'have known'.