Cascading / Dependent dropdown lists using Acrobat DC Standard

This is perfect. Thanks a ton!

I had found an older version of this file which had a bug that reset the dependent combo box selection after saving, closing and reopening the file. The one you have shared seems to be working well. 

Thank you to all who contributed.

Thank you for your response. 

Due to my limited understanding of JavaScript, I searched for another logical but easier way to solve this via Show/Hide dropdown lists and came across this link. In the options panel, check the box that says "Commit selected value immediately" then add your code to the Custom Format Script of the Master dropbox.

Sample I customised to suit my need (posting here to assist others) that seems to be working well so far:

Note that everything after "//" are comments for you to understand the code. Append IF and Else statements similarly for additional dependent dropdown fields that you'd like to show/hide. The only downside I can think of is that I need to create as many dependent Combo Box fields as the number of options in the Master List. Welcome all constructive feedback. 

var v = this.getField("MasterList").value; //Replace MasterList with the Master/predecessor field name
if (v === "Option1") { //Replace Option1 with the first dropdown option value from the MasterList
this.getField("ComboBox1").display = display.visible; //Replace ComboBox1 with the first Combo Box (Dropdown list) field name
}
else {
this.getField("ComboBox1").display = display.hidden;
}
if (v === "Option2") {
this.getField("ComboBox2").display = display.visible;
}
else {
this.getField("ComboBox2").display = display.hidden;
}