B) Listing quality is based on algorithm that factors in things like the title, keywords, photos and bullet points in the top 10 listings. Ideally you want to find niches where listing quality is low (so yours can be much better). Here, a lower number signifies poorer quality listings and more opportunity, and a higher number shows higher quality listings in this niche.
In addition, you must know how much you want to earn by joining affiliate programs. Will it be your main source of income or just an additional one? For the first scenario, you should consider promoting products that are expensive and, consequently, that can bring you a good profit. If you plan on the second scenario, you can opt for affiliate programs that pay for sign ups or affiliate programs that pay daily.