Which the following statements typifies tropical rain forests? a. they are usually composed of at least ten distinct layers, or stories, of vegetation. b. they are found in areas with high accumulations of organic material in the soil. c. they occur in areas with ancient, mineral-poor soil. d. they are known for being only moderately productive.

        The right answer here is option C. They occur in areas with ancient, mineral-poor soil.

         An example of that is Amazonia in Brazil, it's one of the biggest forests on earth, and at the same time, we know its soil is poor, but at the same time it has some special materials that can be found there, such as niobium. This forest is, too, rainy almost all the time, and this many trees maintain the temperature of the whole earth stabilized. These kinds of forests can grow in this soil because of the burlap, that's organic materials from its own trees. It's consumed by them, and through this way, it survives and extends its size when humans don't use its resources too much.

the sugar-phosphate backbone forms the structural framework of nucleic acids, including dna and rna. this backbone is composed of alternating sugar and phosphate groups, and defines directionality of the molecule.