C
插入句独立性强,一般用标点符号将其与其他句子成分隔开。应当特别注意疑问句的插入句,它一般为倒装语序且无任何标点符号,而且整个疑问句应当保持陈述语序。例如:
( 1 ) What should I do first?
What do you think I should do first? (被插入的疑问句原来为倒装语序,插入后成为陈述语序)
( 2 ) Who is singing?
Who do you think is singing? (被插入的疑问句原来就是陈述语序,不需要做调整)
C