Remove question category drop down

Hi,
To remove the question category dropdown, you can add the following code to the style.css file:
.dwqa-list-question .filter .filter-by-category.select { display; none; }
Regards,

Hi, I want this feature as I can see in this page too 

DW Question & Answer Plugin

How can I activate this dropdown category? 
Thanks

At the moment, the plugin has removed the filter by category. This section just shows on the older version of the plugin.