2.or
3.表示对比、转折关系的并列连词有but,yet,whereas,while等。 Jane said she was ill,yet I saw her in the street just now. 简说她生病了,但刚才我在街上看到了她。 He likes pop music,while I am fond of folk music. 他喜欢流行音乐,而我喜欢民间音乐。 Some of the studies show positive results,whereas others do not.有一些研究结果令人满意,然而其他的则不然。