Cells are autonomous which means they are self contained. They are able to carry out their own activities independently for their survival. They are able to synthesis protoplasmic components of a cell from non living matter such as simple organic compounds. They are able to divide into daughter cells as they are capable of producing energy, exchange of gases and replication of genetic material required for division. Every such cell has a limited life span as it grows, divide and then later die but the other cells surrounding that cell may be in a different state of growth. Hence, option D is correct.