This is the Google Form that I use to develop and test the WordPress Google Form plugin.
https://www.gstatic.com/_/freebird/_/js/k=freebird.v.en.wQGEnG7uJ00.O/d=1/ct=zgms/rs=AMjVe6gMWfZqmkx1RFLU8o_Kzo2fCgncGA/m=viewer_base
The following shortcode produces the sample form displayed on this page:
[gform email='on' prefix='wpgform_' form='https://docs.google.com/spreadsheet/embeddedform?formkey=dEJ6cTZidDJPY3B3aW5XeEI4RWVsNnc6MQ' validation='on' captcha='on']