Answer: B) Search engine's web robot
Explanation:
Search engine is basically use the data or information in the webpage and it is also a web base tool which enabled the users for locating the information and data in the world wide web.
It is basically perform various date filtered searches as the web server send the webpage to the search engine web robot. It also include a header which basically contain data in the web page, when it is last modified.
Therefore, Option (C) is correct.