Which of the following is true? a. There are RFCs that describe challenge-response authentication techniques to use with email. b. Filtering for spam sometimes produces a false positive, in which legitimate email is identified as spam. c. Spam relies heavily on the absence of email authentication. d. All of the above.

What is the primary difference between the header section of a document and the body? a. the body is displayed on the webpage and the header is not. b. the header is displayed on the webpage and the body is not. c. the tag for the body is self-closing, but the tags for the headers must be closed. d. the tag for the header is self closing, but the tag for the body must be closed.

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