The correct answer is d. morula.
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A morula is a stage in early development, formed 3–4 days after fertilization. It is a 16-cell mass which forms a solid ball contained within the zona pellucida. A morula develops into a blastocyst.</span>
Answer:
Humans have breached this cycle by digging up fossil fuels and burning them, leading to carbon dioxide building up in the atmosphere faster than natural systems can soak it up. This has led to a net increase in greenhouse gases in the atmosphere, causing the planet to heat up.
Explanation:
1) The answer is <span>bluegreen algae
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Bluegreen algae or cyanobacteria <span>are thought to have started life on earth because they converted the atmosphere that didn't have a lot of oxygen, into an atosphere with enough oxygen to exist life. That </span>oxygen was a product of their photosynthesis.
2) The answer is lightning.
<span>By Primordial Soup Theory, life began as a result of the combination of chemicals from the atmosphere and lighning (a form of energy) to make amino acids. Aminoacids are necessary to build proteins, and proteins are necessary for all the organisms.</span>
<span>The major structure that supplies the cells with nutrients and removes their waste is the circulatory system. The circulatory system is composed of the heart, the blood vessels going from and back to the heart, and the blood that travels inside them. The blood vessels that carry nutrient and oxygen-rich blood to the cells are arteries. They become the thinner arterioles, and then the thinnest capillaries. With the exception of the pulmonary arteries, which carry non-oxygenated blood from the heart to the lungs, all arteries carry oxygenated blood. The capillaries disburse the nutrients and oxygen to the cells and pick up wastes and carbon dioxide, form into the thicker venules, then to form veins, which lead back to the heart (with the exception of the pulmonary veins, which carry oxygenated blood from the lungs to the heart). Veins also differ from arteries in that veins have valves to prevent blood from flowing backward.</span>