How can I open 2 select inputs back to back on mobile

[zootechdrum]

I would like to programmatically open up the select menu when the user completes a previous part of the form. I have a very simple and watered down example that can be found here

Please look at it on mobile
(codepen.io)

The menu seems to pop up but only for a few seconds. How can I make it stay put.

This is the behavior I am trying to replicate on mobile.

[zootechdrum]

@camperextraordinaire

  $cars = $("#cars");
  $("#cars").attr('size', $cars[0].length);

Yeah, I tried the same thing. This does not work on mobile. I am using an Iphone and the menu does not drop down.