You are developing a Universal Windows Platform (UWP) app that will be published to the Microsoft Store.
The app will contain the following method.

JavaScript in the app will call the method.
You need to implement the method.
What should you do first?

A.
Create a Windows Runtime Component project.

B.
Add a class file to the project.

C.
Create a portable class project.

D.
Add the method to the App.xaml.cs file.

Explanation:
By using the Windows Runtime, you can create components (essentially DLLs) in C++, C#, or Visual Basic, and
call into them in a simple and natural way from a Windows Store app that’s built by using JavaScript.

https://msdn.microsoft.com/en-us/library/hh441572.aspx