Which of the following descriptions of keywords in content filtering is incorrect?

Which of the following descriptions of keywords in content filtering is incorrect?
A . Regular expression matching is more flexible and efficient than text matching, but the configuration needs to follow the regular expression rules.
B . Keywords include predefined keywords and custom keywords
C . Predefined keywords are keywords that are manually defined by the administrator and can be identified
D . The minimum length of keywords that can be matched by text and regular expressions is 3 bytes.

Answer: C