Which statement best compares single-celled and multi-celled organisms? (A) Tissues in a single-celled organism are like the cells in a multi-celled organism. (B) The nucleus in a single-celled organism is like the skin of a multi-celled organism. (C) Organelles in a single-celled organism are like the organs in a multi-celled organism. (D) The cytoplasm in a single-celled organism is like the nervous system in a multi-celled organism.