The book is worth ________.
-What heavy rain! -_____ it is raining, the farmers are still working there.
-I didn’t know _______.He looked so sad yesterday.-Maybe he failed his exams.
Shanghai Zoo is very famous. Every year ______ people visit it.
--You have been to Shanghai, haven’t you? --_______. I have only been to Nanjing. I plan to visit it this summer.
--Who is knocking at the door?-It ______ be Mr. Wang. He always knocks at the door so loudly.