The boy was really lucky ----? To fill the gap we need ---
The boy was really lucky ----? To fill the gap we need --- Correct Answer Wasn't he?
Affirmative বাক্যের tag question হবে negative আর বাক্যে be verb থাকলে এর negative form ব্যবহৃত হয়। অর্থাৎ was't he ? হলো সঠিক tag question.