What two things are needed to successfully implement a layout?

In a non-SXA website where you are using Sitecore MVC, you are working on the presentation for awebsite, starting with the layout.

What two things are needed to successfully implement a layout? (Choose two.)
A . A layout.cshtml file
B. A layout definition item
C. A standard values item
D. A presentation details settings item
E. A main placeholder

Answer: A,B