How does the top-down approach differ from the bottom-up approach in language processing?
选项：

A:Bottom-up processing is more effective than top-down processing in speech synthesis.;
B:Bottom-up processing utilizes all information one has in speech perception.;
C:Top-down processing uses one's existing knowledge and the incoming speech signal.;
D:Top-down processing is more efficient than bottom-up processing in speech comprehension.