A. The internet, since we cannot see it B. That part of the internet, which is hidden from the search engines C. The telecommunication signals which are not seen D. The failure in accessing the web pages
The invisible web is also referred to as the deep web. This is B. The part of the internet which is hidden from search engines. You should realize that there are a lot of things on the internet that is still not seen because of various reasons. There may be websites that are created solely for private purposes and they should not be visible through typing some keywords on the search engine bar.
Some people think that information is not found because of people’s limited research skills but there are also some that are meant to not be found online. There are also some things that can only be searched through specific keywords that are unrelated to what you will actually see.