Multi-choice problem: Continue writing the next sentence in this paragraph:

How to create a mockup of your app idea by yourself
Provide a brief but a clear description of your idea which includes the purpose, scope, goal and other assumptions.
Target a niche group of audience for your app.
This is to get the best out of your app and know all it's pros and cons inside out.

Choices:
a). Therefore, describe the target demographic of your app, your potential customers. Create an interactive prototype of your app.;
b). Don't rely purely on your friends to have the ball rolling; target the resources needed to take all the shape. Also, don't be shy about making a list.;
c). In order to give your app the unique brand name and visual appeal, you need to work on the style and content that surrounds it. If your app can be hidden on wikipedia, bring it out in west west.;
d). The range from 15 to over 1500 people is for start you go. Build a stable audience with a good idea of the goals and objectives of your app.;
a).