You can just hide each of the submenus:
If you want all of the submenus to be hidden except for the first one, you can use:
For example: https://jsfiddle.net/h30gd9mo/1/
@Paul_Wilkins <h3> About is open !
Paul gave you the instructions for hiding all the dropdowns in the post above. Just change the first line of the JS to the first version, which which will hide all, rather than the second version, which doesn't hide the first section.