How to make the dynamic drop down hide or show as per selection

I created a drop down:

  1. adtype_list with two options
    a. Advertorial
    b. Advertisement

  2. advertisement_type_list with two options
    a. Full length
    b. Half length

This is how I added the layout
–added a dynamic drop down
–choose advertisement_type_list
—added dropdown type 1 as the parents in the text box

What I exactly want is to display the options in drop-down 2 only when users select the option advertisement in option 1.
For now the options in drop-down 2 is shown whether I select advertorial or advertisement in the dropdown 1 .

How to meet my requirement and is it possible to display the dropdown 2 only if the advertisement in selected in dropdown 1 else hide it .