You use Natural Language Understanding in your bot. You create a language understanding template in a file format that intents and utterances are mapped. You use this file format to test your bot locally using Bot Framework CLI. 
To test your model using Bot Framework CLI command “bf luis:test”, which supported file format will you provide as input source. (select one answer choice)

Answer options:

A..lu
B..lg
C..qna
D..dialog

Correct Answer: A
Option A is correct because .lu file format and .json file format are supported as input file formats for testing locally using Bot Framework CLI. Here is a quick sample of the .lu file format:
<pre class="brush:java;">****************************************************
&gt; Use "&gt;" to create a comment in your .lu files.
&gt; Use multiple comment "&gt;" characters to define outlining
&gt; sections in the file to help you organize the content.
&gt;&gt; Primary intents
# Greeting
- Hi
- Hello
- Good morning
&gt;&gt; Secondary intents
# CheckWeather
- What`s the weather in London next week?
****************************************************
</pre>
Option B is incorrect because .lg file describes language generation templates with entity references and their composition.
Option C is incorrect because .qna files contain Markdown-like text based definitions for QnA Maker.
Option D is incorrect because dialogs provide bot functionality and have many components such as source code, business logic and training data.
Reference:
To learn more about .lu file format in bot framework, use the link given below: 

https://docs.microsoft.com/en-us/azure/bot-service/file-format/bot-builder-lu-file-format?view=azure-bot-service-4.0