Classify each of the following substances as an element, compound, or mixture. (a) Calcium chloride, used to melt ice on roads, consists of two elements, calcium and chlorine, in a fixed mass ratio. (b) Sulfur consists of sulfur atoms combined into octatomic molecules. (c) Baking powder, a leavening agent, contains 26% to 30% sodium hydrogen carbonate and 30% to 35% calcium dihydrogen phosphate by mass. (d) Cytosine, a component of DNA, consists of H, C, N, and O atoms bonded in a specific arrangement. (a) Calcium chloride Element Compound Mixture (b) Sulfur Element Compound Mixture (c) Baking powder Element Compound Mixture (d) Cytosine Element Compound Mixture