They form hydrogen bonds between opposing dna which forms the twister ladder of dna
The right answer is D) photosynthesis in plants
Cellular respiration does not produce oxygen, it consumes it rather. The same for the respiration of animals and the human being.
The degradation of organic matter does not produce oxygen.
Photosynthesis is the only one of these proposals that produces oxygen, and this process belongs to the plants.
The Organ is the largest biological level.
First there is a cell, and a bunch of cells make up tissues, and a bunch of tissues makes up an organ, which makes up a organ system (like the digestive system), which makes up a organism.
Molecule is more of a chemistry thing, so it's not included in Biology, the smallest unit of life is a cell.
