Answer 1

https://www.sololearn.com/discuss/327674/?ref=app

Answer 2

So I take it that no one really knows why it hasn't been added?

Answer 3

Not the same, you see C is the mother and father of most modern programming languages, especially the ones taught here on sololearn. c++ c# java pho python... It just seems so natural that it would included here as well seeing how it is still widely used today

Answer 4

SoloLearn has the C course now:
https://www.sololearn.com/post/34110/?ref=app
Moreover, C language is available as a challenge weapon and you can submit quizzes😊🎉