The four letter code in dna includes four different types of

There are four basic types of unit: A, T, G, and C.

Explanation:These letters represents the type of base each unit carries: adenine, thymine, guanine, and cytosine. The sequence of these bases encodes instructions.

rain is the best answer

imagine a line passing through the center of earth that goes through both the north pole and the south pole. this imaginary line is called an axis. earth spins around its axis, just as a top spins around its spindle. this spinning movement is called earth's rotation. at the same time that the earth spins on its axis, it also orbits, or revolves around the sun. this movement is called revolution.