Had I seen him there -
Had I seen him there - Correct Answer I would have talked to him.
Had + sub + past + participle দ্বারা কোনো Sentence শুরু হলে, অপরটি Perfect conditional হয় অর্থাৎ Sub - এর পর Would have / could have /might have বসে। তারপর Verb – এর past participle form হয়। সুতরাং শূন্যস্থানে I would have talked to him বসবে।