D) The Earth was hit by a one or more objects from space 65 million years ago. The iridium layer shows an extraterrestrial cause for the extinction at the Cretaceous Tertiary boundary, discovered by the Alvarez family. The first discovery of this layer was in the Bavarian alps, in Lattengebirge. The Alverez family proposed that the extinction of the dinosaurs was due to a large meteor hitting the Earth at the end of the Cretaceous period, marking the KT boundary with this clay layer which has a high content of iridium. Iridium is not common on Earth, but is common in meteors.
Systemic circulation is the circulation of blood through<span> the arteries, capillaries, and veins of the general system.
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Answer: Dr. Balduzzi says it's important to remember that sweat is your body's main evaporative cooling system -- kind of like an internal fan. If you're exercising in cold air, your body doesn't need to produce as much sweat to keep you cool.
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