Dna contain thymine which is one of the 4 bases.
Topsoil is the A horizon in figure 7-1.The most leaching of minerals occurs from the A horizon into the B horizon. The C horizon shown in figure 7-1 is most like the parent soil, and <span>the A horizon in figure 7-1 contains the most humus.</span>
Explanation:
1. it is easier for yonger ones for a change than others
2.yout only need SI unit