Censorship typically refers to the suppression of speech, public communication, or other information. The main categories of censorship include religious censorship, which involves controlling information based on religious beliefs; moral censorship, which restricts content deemed immoral or offensive; and military censorship, which involves controlling information for national security reasons. Environmental censorship, while it may involve the suppression of information related to environmental issues, is not traditionally classified as a category of censorship in the same way as the others mentioned. Therefore, it is the correct answer to the question.