Roman is my colleague. I ____ him for nine years.

The correct answer - খ) have known.- Complete sentence: Roman is my colleague. I have known him for nine years.অতীতে সংঘটিত হয়ে কোনো কাজ বর্তমান সময়ে চলছে এরূপ বুঝালে Verb এর Present Perfect Continuous Tense হয়।কিন্তু see, watch, understand, know, be, have ইত্যাদি verb এর সাধারণত Present Perfect Continuous Form ব্যবহৃত হয় না, এর পরিবর্তে Present Perfect Tense ব্যবহৃত হয়।Structure: Subject + have/has + verb এর past participle + Extension.যেমন:- He has been in London for three years.- I have seen him for two decades.Source:Learn English Online, British Council.