Correct answer is (c) css_dir
For explanation: sass_dir gives folder name for the sass or SCSS style sheet to be stored. css_dir property specifies the folder name where CSS style sheets should be saved. We can change css_dir value to something like css or styles, but we should also change the folder name in the working directory to the one that matches the change. A folder name where javascript file are stored is given by javascript_dir. The output path in compiled CSS is given by relative_assets.