The systems are most responsible for providing cells with oxygen and removing the carbon dioxide. a) excretory and muscular b) digestive and excretory c) skeletal and respiratory eliminate d) circulatory and respiratory

actually the answer is c

producers within ecosystems are essential as they are at the base of the food chain. plants are examples of producers. they use the process of photosynthesis to capture light energy and use it to convert simple inorganic substances (carbon dioxide and water) into organic substances (glucose).