An independent clause is found in a compound sentence and occurs when each clause can operate as a complete sentence in it's own right.
A subordinate clause adds information but does not serve as a sentence in it's own right for example, it relies on the main clause within the sentence to make sense.
The sentence you construct would be a compound sentence and would read:
The journalist met a source at the hotel SO THAT he would get the facts for an article.
Answer:
The evidence comes come a credible, reliable source.
Explanation:
The passage states how the birthmark on Georgiana's cheek causes her to be "countenance even hideous" therefore the answer is B). the birthmark on Georgiana's cheek.