(1) We tried to fix it and there was nothing we could do. (and 改为 but，因此处语意转折)
(2) I told Mother, Father, Sister, all my friends here what a great time I had. (all 前加 and，表示并列关系)
(3) It is a very important exam but I can’t afford to fail it. (but 改为 and / so，此处表因果关系，并非转折关系)
(4) She was smiling but nodding at me. (but 改为 and，因此处并无转折之意)
(5) It looks as if my parents treat me as a visitor and a guest. (and 改为 or，a visitor 和 a guest 应是选择关系，意思是“好像我的父母亲把我当作一个来访者或一个客人”)
(6) The food was expensive and the service was good. (and 改为 but，此处意义发生转折)
(7) I’m the captain of our school team so with my fellow players we’ve won several games. (so 改为 and，表并列关系)
(8) My grandma was the best cook in the world but could make the most delicious dishes.(but 改为and，此处表示并列，而不是转折)
(9) So once you’ve started collecting seriously, you… (So 改为 But，因为前后是转折关系)
(10) Clever as she is, but she works very hard. (去掉but，因前面已有引导让步状语从句的连词 as(=though 虽然)，千万不要受汉语句式“虽然……但是……”的影响，而重复用连词)
(11) I teach them, play with them, but watch them growing up.(but 改为and，因为 teach / play 与 watch 是并列关系，而不是转折关系)
(1) Do you want a bath at once, and shall I have mine first?
(2) Are you going to clean your car before and after supper?
(3) Hurry up, and you’ll be late for school.
(4) She never said she was rich, and she was.
(5) Mr Smith worked very hard so without any success.
(6) Everyone asked me to go, but I went.
(1) and 改为 or，or 在此表选择。
(2) and 改为 or，or 在此表选择。
(3) and 改为 or，or 在此表示“要不然”、“否则”。
(4) and 改为 but，but 在此表示转折。句中的 she was 为 she was rich 之省略。
(5) so 改为 but，此处语意转折。
(6) but 改为 so，so 在此表示因果关系。