sentence2_structure: a global scale<>,<>plants$$$a global scale<>, plants and<>other photosynthetic organisms$$$plants<>and<>other photosynthetic organisms$$$plants<>and other photosynthetic organisms have generated<>all$$$other photosynthetic organisms<>have generated<>all$$$other photosynthetic organisms<>have generated all of<>the oxygen$$$other photosynthetic organisms<>have generated all of the oxygen in<>the air$$$all<>of<>the oxygen$$$all<>of the oxygen in<>the air$$$the oxygen<>in<>the air
sentence1: In essence, it s a small-scale power plant that generates electricity using oxygen from the air and any fuel source that contains hydrogen, such as natural gas or propane.
sentence2: On a global scale, plants and other photosynthetic organisms have generated all of the oxygen in the air.
question: On a global scale, plants and other photosynthetic organisms have generated all of what element in the air?