in your study materila its given that monopolist has perfct know;edge while in comparison it shows imperfcet know;edge so which one is accurate ?plsss tell me urgbt

Both the statements are correct. When we say that a monopolist has perfect knowledge, we mean that the monopolist who is a single seller in the market has complete knowledge about the market conditions. But other firms and customers may not have perfect knowledge about the monopoly firm or the market. This is the reason which restricts other firms from entering the market Therefore, we can say that the monopolist has perfect knowledge but the market has imperfect knowledge.  

Also, whenever we make comparisons between different market forms our focus should be on the market as a whole. But when we are listing the features of a monopoly firm, we must focus on the Monopolist only.