有道理!附上ron神的解释:"after having VERBed" is, in general, a redundant construction -- the word "after" is already there, so "having" doesn't contribute anything. if you see this construction, you should generally be able to replace it with "after VERBing".
看到正确答案,突然想到RON讲的 "A modifier must be either blocked off by commas or not blocked off by commas. You cannot block off a modifier with a comma on one side but not on the other".
正确答案C里面不是刚好犯了这个错误吗?
C. which have increased five percent during the first three months of this year after falling
只有前面没划线部分有Comma,后面没有comma啊?