Change the "selected" of an based on the "selected" of the previous
Dear my friends...I am stil new in JavaScript. I want to build an option depends on the entry of its previous option in a form.But it does not run as I expect. Please tell me what is my mistake.Thank you very much in advance.==========This is my current code.==========
Change the "selected" of an based on the "selected" of the previous
Linear Mode
