—What’s the matter with you? You look so worried.-- I don’t know ___________ the problem.
Sun Tao has had a_______ English course, but he still doesn't know
--Jack's never worked hard at English, _______? -- _______ , so he can't answer the question in English, I think.
--I have been working hard at math. However, I can't get good marks in the exam. --Go on studying hard. And I think your dream will
--Why not _______ to London for holidays? --Good idea.
--_______ do you like this book? --I like it because it can remind me _______ my childhood.