Pentaprism is a five sided prism with two silvered surfaces giving a non-stop deviation of all rays of light through 90 degress. Used in viewfinders of single-lens reflex cameras
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).
Answer:
b is the right answer. she posts messages that avoid slang and text language
