Drop Down Menu - Input Boxes

[Royalty]

Hello everyone, how would I make something like if a user picks a different option from the drop down menu, each input box will be different. Example:

<option value="" selected="Select A Car"></option>
						<option value="audi">Audi</option>
	  <input name="audi" type="text" id="audi" size="30" placeholder="Audi R8" class="required">
[/CODE]

[b]BUT [/b]if for example the user DOES NOT pick "Audi" and they pick BMW, the input will be like this:

[CODE]
<option value="bmw">BMW</option>
<input name="bmw" type="text" id="bmw" size="30" placeholder="BMW M5" class="required">
[/CODE]

So each option will show a different input box. How do I do this?