<span>The troposphere is the lowest portion of Earth's atmosphere. It contains approximately 75% of the atmosphere's mass and 99% of its water vapour and aerosols. The average depth of the troposphere is approximately 17 km in the middle latitudes. It is deeper in the tropics, up to 20 km, and shallower near the polar regions, approximately 7 km in winter. The lowest part of the troposphere, where friction with the Earth's surface influences air flow, is the planetary boundary layer. This layer is typically a few hundred meters to 2 km deep depending on the landform and time of day. The border between the troposphere and stratosphere, called the tropopause, is a temperature inversion.</span>
Population decrease and extinction
Covalent bonds form by sharing of electrons and ionic bonds are formed by donating electrons.
<h3><u>Explanation:</u></h3>
Covalent bonds are formed between less electronegative and less electropositive atoms of elements. These atoms are unable to donate the electrons or accept them fully because of their affinity towards these electrons.
Ionic bonds are formed between the more electronegative and electropositive atoms of elements. They fully donate or accept the electrons to fulfill their octet. Thus, they are only attracted towards each other by means of electrostatic force of attraction. There’s no actual bonds present between the atoms unlike those in the covalent atoms.
Answer:
A. Liquid rock hardens into solid rock as it cools underground.
Explanation:
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