C没有任何的模糊的意思。A并不是语法prefer的用法，如下。
从网上查到的，解释了A为什么没有C好：
Participial phrases are short phrases that appear
at the beginning of a sentence or the end of the sentence. These participial phrases should
always be set off from the main clause with a comma. The action that is occurring in these participial phrases
should relate back to the subject.（并不是must，所以有了歧义的根源） That is, the subject of the sentence should be doing the action. If this is not the case, the result is a dangling modifier.
Incorrect: A large twig floated over and jabbed him, swimming against the tide.
Here swimming against the tide is not something that the twig is doing. Twigs don't swim. They float.
However, it appears as if swimming against the tide is modifying him (the final pronoun in the main clause). While some grammarians might not find anything objectionable about this practice, generally speaking, participial phrases (both at the end of and in front of the main clause) should refer back to the subject.（并不一定是错误的，但确实不清不楚！）
When a participial phrase is attached to the end of a sentence and it is modifying the last word of the sentence (a noun), it
may be acting like a reduced relative clause as well. In this case, refer to the rules for restrictive and non-restrictive clauses for punctuation. （用restrictive or non-restrictive clause解决了这个问题！）
Example: Harold invented his own god, laughing maniacally at the sight of a face in a cloud.
The question here is
who is laughing maniacally. Punctuated as it is now, laughing maniacally at the sight of a face in a cloud is a participial phrase that modifies Harold. However, it could be seen as a reduced relative clause that is modifying god. This relative clause is restrictive because laughing maniacally would specify what kind of god Harold had invented. Therefore, use no comma.
Correct: Harold invented his own god, who was laughing maniacally at the sight of a face in a cloud.
-- by 会员 BeBrave2011 (2010/10/19 12:17:25)
