When writing new App in Tropo, in what format should the App Scripts be saved?

When writing new App in Tropo, in what format should the App Scripts be saved?
A . .js
B . .json
C . .mp4
D . .xml

Answer: B

Explanation:

Tropo’s WebAPI is built around a request/response model using JSON as the data format; Tropo sends JSON to your application, your application responds with JSON instructions telling Tropo what to do, Tropo sends back results, and so on.

https://www.tropo.com/docs/webapi/creating-your-first-application