14.5 only在句首要倒裝的'情況
Only in this way, can you learn English well.
Only after being asked three times did he come to the meeting.
如果句子為主從複合句，則主句倒裝，從句不倒裝
Only when he is seriously ill, does he ever stay in bed.
14.6 as, though 引導的倒裝句
as / though引導的讓步從句必須將表語或狀語提前 （形容詞, 副詞, 分詞, 實義動詞提前）。
注意：
1) 句首名詞不能帶任何冠詞。
2) 句首是實義動詞, 其他助動詞放在主語後。如果實義動詞有賓語和狀語, 隨實義動詞一起放在主語之前。
Try hard as he will, he never seems able to do the work satisfactorily.
注意:
讓步狀語從句中，有though，although時，後面的主句不能有but，但是 though 和yet可連用。
