Question #6b --- ANSWER
This question calls for understanding a concept, not just remembering facts. It requires that you think about tetrads in a different way. Of course, it's assumed that you know what "diploid" means (which is vocabulary). So the question asks about the relationship of tetrad number to diploid number.
Ask yourself: what is a tetrad? 4 chromosomes bundled together? Any 4? (No) So, what does a tetrad represent? We specified this in class, but we started with the parent cell containing its diploid number of chromosomes and went forward. Here the question gives you the tetrads already present and wants to know what was that diploid number before tetrads came into existence. So, what does a tetrad represent? Answer: a duplicated pair of homologous chromosomes. Then, each tetrad that you see in meiosis corresponds to one homologous pair that was present before the cell prepared for meiosis. 12 tetrads corresponds to 12 homologous pairs, which means that the diploid number is 24.
Most people will stumble on such a question, even though it doesn't introduce anything new beyond what we covered in class. It checks to see whether you really understand what tetrads are, which goes beyond just memorization. Now that you've worked your way through it, where did you get stuck trying it yourself? and why?
Note also that the same question could have been presented in a multiple choice format, with many choices (numbers), including "none of these" or "impossible to say" among the choices. The point? Multiple choice format won't help the person who doesn't know the vocabulary and doesn't understand the concept involved.