Responsiveness is not possible unless HTML5 is enabled.
A Stacked Dynamic Layout is not something that by itself can be responsive - several such layouts side-by-side within an in-line layout would react responsively within a responsive UI but that is an effect not a cause.
Answers 3 and 4 are overly generic.
Auto-generated interfaces are a distant-ancestor pre-requisite to having a responsive interface but without HTML5 you would never get there.
Yes the quiz in the Introduction to Responsive UI lesson states that "Using a Stacked Dynamic Layout to group data elements" is the correct answer.. Can you please explain why that is the correct answer ? In my understanding, is it that "Enabling the Application to render in HTML5 Document Type" is compulsory to achieve responsiveness. Which in that case you cannot say helpful. But as the SSA guide says, "..,layouts can be made responsive using Layout groups." and further more it states "PRPC support four formats by default: 1. Tab, 2.Accordion, 3. Stacked, 4.Menu". So does the question mention "Helpful" as in relation to the "Usage" ? Where in this case the usage of Stacked Dynamic Layout is helpful to achieve responsive user interfaces ? Thank you. :)