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During the Devonian period,plants evolved which of the following key innovations to overcome the harsh,dry conditions of life on land and flourish? A) waterproof cuticle, vascular systems, structural support tissues, leaves, roots, seeds, and specialized reproductive structures B) amniotic eggs with a hard shell, photosynthesis, flowers with protected seeds C) flowers with protected seeds, photosynthesis, hard-shelled amniotic eggs D) photosynthesis, flowers with protected seeds, waterproof cuticle

The Cambrian explosion resulted in the evolution of more than 17,000 species of an animal known as the trilobite.The sheer number of trilobite fossils found in modern times suggests that trilobites were abundant,perhaps the rulers of the seas.Today,no living descendants of this group exist.What happened? A) Trilobites evolved before the first mass extinction, so it is possible that any of the five mass extinctions could have wiped out the entire group. B) In order to disappear from the planet entirely, trilobites must have undergone the process of adaptive radiation. C) It is unlikely that trilobites could have survived the increase in atmospheric oxygen once the process of photosynthesis had evolved. D) Being so plentiful, trilobites must have been the major food source for terrestrial dinosaurs. The extinction of the trilobite may have caused the mass extinction of dinosaurs.