Enzymes are biological molecules (typically proteins) that significantly speed up the rate of virtually all of the chemical reactions that take place within cells.
Answer - C. Their life span is too short
Reasoning - It is because R-organisms have structures that can not keep up the pace for its survival needs and reproduction can sometime alter the gene and chromatic DNA.
The answer is cotton. It is natural because it is grown and easily woven in to clothes :)
It is true that one of the key factors that pushes the successional process along toward a climax community in aquatic ecosystems is sedimentation.