Adding options when loading LaTeX class in org-mode

Problem and solution

When loading LaTeX class you may sometimes want to add specific options. For example you may want to have 16:9 aspect ratio which in plain latex is added with:

\documentclass[aspectratio=169]{beamer}

To add this option when using (for example) beamer in org-mode, just do

#+STARTUP: ...
#+OPTIONS: ....
#+LATEX_CLASS: beamer
#+LATEX_CLASS_OPTIONS: [presentation,aspectratio=169]
...

This solution can be found here.