It helps the plants create oxygen for us to breathe
The Cretaceous–Paleogene (K–Pg) extinction event (also known as the Cretaceous–Tertiary (K–T) extinction) was a sudden mass extinction of three-quarters of the plant and animal species on Earth, approximately 66 million years ago.
Nitrogen fixation is a process in which nitrogen (N2) in the Earth's atmosphere is converted into ammonia (NH3). Atmospheric nitrogen or molecular dinitrogen (N2) is relatively inert: it does not easily react with other chemicals to form new compounds.
The answer is A because genetic means it comes from your genes/parents genes so you know it’s either A or B because they both state something about your parents passing it to you. But you know it can’t be B because chloroplasts are only in plants and A says chromosomes which are in humans and relate to genes so we know it must be A.
The electron transport chain is part of the overall processes of cellular respiration and photosynthesis. The solution is A.