Xác định lỗi sa và sửa lại : 1 . Someone has been smoking in this room because it is dirty 2.look. her eyes are red . she had been crying 3. don't worry , i hope everything is going to be fine soon 4 last year , my son was lost among the crowd while we have gone shopping 5. almost 300 million people had visited america's national parks every year 6 they have studied english before they went to London 7 they has got married for 30 years by the end of this month 8 up to now , there had been no woman being chosen the us president 9 when i walk past the park , i saw some children play football 10 Ann and Suan have known each other during they were at school 11 after he graduates from university , he joined the army 12 up to now , there had been no woman being chosen the US president Giúp mình với