Ionic bonds are formed due to tendency of a metal to donate an electron and tendency of non metal to gain an electron.
Answer:The Ordovician and Cambrian Periods are referred to as the "age of invertebrates", with trilobites abundant. In this period, brachiopods became more abundant that the trilobites, but all but one species of them are extinct today.
Explanation:
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C. development of a liquid propulsion system is the answer
Answer: BIt shows that a lunar eclipse occurs when the Earth casts a shadow over the moon.