Answer:
Index fossil, any animal or plant preserved in the rock record of the Earth that is characteristic of a particular span of geologic time or environment.
Explanation:
True
Lies just beyond the continental slope is the open ocean zone and it has three subzones namely the epipelagic(sunlit zone), mesopelagic(disphotic zone) and bathypelagic zones(aphotic zone). The oceanic zone covers 65% of the ocean's water and where different types of terrains can be found. From deep trenches, deep sea volcanoes and basins. A variety of sea creatures can also be found on each subzone.
Metals like sodium, potassium, magnesium, etc. are extracted by electrolysis of their chlorides in molten state.
These metals are not extracted by reduction of their oxides with carbon because:
Carbon has less affinity for oxygen than these metals
Carbon is a weaker reducing agent than these metals
These metals easily form oxides with oxygen, their oxides are very stable. Affinity to the oxygen is one the greatest of all elements.
Reducing agent is element or compound who loose electrons in chemical reaction. Sodium, potassium, calcium and magnesium are very strong reducing agents because they easily loose one or two valence electrons.
Electrolysis is a chemical methode that uses electric currents for chemical reactions.
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Answer:
Bacterial cell, cell with a nucleus, multicellular organism
