This history book is of great value.— Exactly. _____ can be enjoyed from it ______ you have a deep understanding of it, however.

5．—Do you feel Professor Wu’s speech on finance easy to understand?—Just the opposite. It’s _______ for me.

“I’ve told you a million times _______ my belongings alone!” shouted Paul angrily. [ ]

Would you like to go for a picnic with us—_______, but I’m too busy.

20. When Jack arrived, he learned Mary ____ for almost an hour.