I thing the answer is A but I’m not sure.
The word venal is an adjective which means that something or someone can be bribed or corrupted. In this case, the word venal means that Randall's immoral attitude or character will serve as a proof against him in trial. That is to say, his usual wrongdoing will be the one which ultimately will condemn him.
Answer: The addition of able turns them into adjectives
Explanation: Noticeable- it becomes an adjective, describing something that can be easilt seen.
Believable- it also becomes an adjective, describing omething that can be easily believed or credible.
Scrooge is able to fly because of Magic