For part (a), the answer is yes. If the natives are both knights or both knaves, they will both answer "yes" to the question. If one of the natives is a knight and the other one is a knave, they will both answer no to the question.
For part (b), there is always an odd number of knights. If A is a knight, then the other two are both knights or both knaves, because they are the same. If A is a knave, the other two are one knight and one knave, because the knave is lying. In both cases, there is an odd number of knights.
For part (c), you can use the question in part (b). "Are the other two the same type?" Using this question, if you get yes, no matter if the one you asked is a knight or a knave, there are an odd number of knights, which answers the question. If the person says no, then there are two knights.
For part (d), B is a knave, and A could either be a knight or a knave. The statement "B is a knight is the same as I am a knave" sounds confusing. Just split the statement into two parts: "B is a knight" and "I am a knave". The words "is the same as" tells you that the true/false component of each of these is the same. If one is false, the other is false. If one is true, the other is true. Therefore, if A is a knight, both parts of the statement are false, and the middle words "is the same as" makes the statement as a whole true. If A is a knave, the true/false component of each of the statements is different. "I am a knave" must be true and "B is a knight" must be false. Therefore, A can either be a knave or a knight, and B is always a knave.
First, your symbolic translations of Bart’s and Zed’s statements are incorrect. Bart actually said $$\text{Ma}\land\text{Ze}\;,$$ and Zed said $$\text{Bo}\land\text{Ma}\;.$$
A quick way to solve it is to suppose that Bart is a knight. Then he’s telling the truth, so Marge and Zed are also knights. But that’s impossible, because Marge said that Zed is a knave: if she’s a knight, she’s telling the truth, and Zed isn’t knight. Thus, Bart cannot be a knight and must therefore be a knave. Can you finish it from there?
Best Answer
Well, let's run through the possibilities.
Case 1: A knight
In this case, B is a spy and C is a knave.
Case 2: A knave
In this case, B is not a spy, and thus a knight.
Case 3: A spy
In this case, C is a knave, and B is a knight.
Thus, the knight is either A or B.
Now let's think about B's statement. Case 1 is a valid possibility, and so is Case 2 (ignoring B's statement). Thus, we can't determine the knight without B's statement, and thus, B is not telling the truth.
Thus, A is the knight, B is the spy, and C the knave.