only 短语置于句首必须倒装吗
■“only+状语（副词、介词短语、从句等）”放在句首时，句子要用倒装语序。如：
Only in this way can we learn English. 只有这样才能学会英语。
Only then did I understand what she meant. 只有到那时我才明白她的意思。
Only when he is selfless can a man be fearless. 只有无私，才能无畏。
Only if a teacher has given permission is a student allowed to enter this room. 只有得到教师的允许，学生才可以进这间屋。
■ 若only后接的不是状语，而是主语或宾语，则通常无需倒装。如：
Only those who had booked in advance were allowed in. 只有那些预先订票的人可以进去。
Only part of his story is true. 他说的事只有部分是真的。
Only his sister he saw there. 他在那儿只看到他妹妹。