Question: Along with DOM traversal and manipulation, jQuery offers several general-purpose helper functions that fill in some JavaScript gaps, especially before ES2015. Which is NOT a jQuery utility function?

1. `jQuery.each`, a general purpose iterator for looping over arrays or objects
2. `jQuery.isNumeric`, which can check whether its argument is, or looks like, a number
3. `jQuery.extend`, which can merge objects and make complete deep copies of objects
4. `jQuery.isMobile`, which can tell whether the user is using a mobile browser

Answer: The correct answer of the above question is Option D:`jQuery.isMobile`, which can tell whether the user is using a mobile browser