Answer:
a) C.
b) B.
Explanation:
Remember that the premise is a statement that will led to a conclusion and justifies it.
a) In the sentence "He refused to testify by invoking his Fifth Amendment rights, so he must be guilty" the premise is: "He refused to testify by invoking his Fifth Amendment rights" because it follows from this that, therefore, he must be guilty (by not testifying, the person who said this reaches the conclusion that he must be guilty).
Thus, the correct answer is C.
b) Briefly describe how the stated fallacy occurs in the argument.
In this argument, the conclusion leaves no place for another outcome (because the conclusion is that he MUST be guilty), therefore it is stated as if being guilty is the only possible conclusion.
Thus, the correct answer is B.