听句子,从所给的A、B、C三个选项中选出一个最佳应答。 ( )1. A. I'm sure you will. ( )2. A. By four o'clock. ( )3. A. It's hard to say. ( )4. A. Of course we can. ( )5. A. Thank you. B. It's frustrating. B. By car or on foot. B. You'd better ask the teacher for help. B. That sounds good. B. The same to you. C. Is it true? C. By working with friends. C. I'm sorry. I only know a little English. C. I'm not sure. C. I'm happy to know that.