If you want to avoid JS you would have to make it a multi step form with the email field on the second page and conditionally show it using keyword modifiers based on the response to the previous question on step 1.
I would still recommend using JS as it wouldn’t require much to get it working that way and it would save you having to split the form into 2 pages.
Modify your requirements to validate the Email field to be filled in if yes to question 2.
Expected outcome:
If the user selects “Yes” and does not enter an Email, an Error Message appears.
If they Select “No” and no email entered the form will be submitted.
How to
Use a Select type question for "“Please contact me with a response” and add values to each Text (answer). Yes = 1 No = 2
Simple Validation Rules
Have the Email question set to Required Entry = Required.
Enter a message in “Custom Required Error” such as “You have not provided your email address”.
Then tick the box to add a condition to this validation rule.
Select the question 2 (asset ID).
Select the “is less than” option and enter number “2” minus quotation.