"a. After the rain ended, the sky became blue" would contain an independent clause and a dependent clause, which makes it a complex sentence, since the latter half wouldn't be the same without the former half.
"The Snow Queen"
This is a famous fairy tale written in 1844 by<span> Hans Christian Andersen who was a Danish author. This is an original fairy tale.
The story got such fame that it is always included in the story collections of Andersen and in almost every illustrated book printed for children. </span>
