Scout, I’ve never read the book or seen the movie but I’ve heard of it so many times.
Sorry for such late an answer, but I believe its A) Predicate Nominative.
The proper way to write the sentence would be "However, no one believed rumors about the Komodo dragon either." Since commas are used after words like "first, second, third, then, finally, however, but..." there would only be 1 comma in this sentence.
I hope this helps!!
I believe the answer is tense