The answer is A. Many compounds are comprised of very different elements. For example, Sodium is a highly reactive group 1 solid metal that combusts when in contact with water, and Chlorine is a reactive group 17 gas that is used in the treatment of pool water; however, when you put them together, you get quite a common, non-toxic food additive: salt. Elements and compounds can sometimes resemble each other, but it certainly isn’t uncommon to see large differences between the two.