<span>He feels happy, but he also feels worried.</span>
The purpose of an introduction in a paragraph is to introduce the subject (of the artical, text,essay,ect...) and grab the reader's attention (on the topic).
We can't see underlining here, but here, I think this will be helpful:
"I read a novel" would be the intependent clause: it does not need the other one to be complete.
"until the guests arrived" is the subordinate clause: it needs the independent, main clause to be complete.
B. sectionalism is used to mean one's loyalty to their geographical region