Which of the following BEST characterizes gas exchange in animal versus plant metabolism: Animals take in O2 and release CO2. Plants take in and release both O2 and CO2. Both animals and plants take in and release O2 and CO2. Animals take in O2 and release CO2. Plants take in CO2 and release O2. Animals take in and release both O2 and CO2. Plants take in CO2 and release O2.