BMP (Bitmap). I may be wrong. I'm sorry.
Answer: C. File encryption
Explanation: To ensure security and privacy of files and its content, encrypting the file may be an option. File encryption refers to a process of ensuring the security and privacy of individual files so as to prevent unauthorized access to the content. File encryption works by setting up a security key which will be requested or needed when the file is being clicked such that only users or individuals with the authorized pass code or password can open and read its content or modify the file, this is called file decryption.
You're writing code in 2018 ... a lot of code editors and IDEs have linting built-in, smart autocomplete functionality, etc.
Given the fact that xhtml has mandatory rules, you just need a code editor/plug-in that has strict guidelines for code completion/error handling regarding xhtml ... use VScode editor (you'll definitely find a linting plug-in for html/xhtml linting).
