B. Each of the following sentences contains ONE mistake. Find it out and correct it. 1. Henry mustn't be at home because he phoned me from the farm just now. ( ) 2. Jack is a bilingual person. He may speak English and Japanese. ( ) 3. Mary can know the answer to the question. I'm not sure. ( ) 4. You mayn't tell anyone about this — it's a secret. ( ) 5. Mother is out, so I must look after the shop. ( )