19. at the end of this period, 96% of all life went extinct. this set the stage for reptiles to really take hold in the next era. * cenozoic carboniferous permian quaternary 20. this is the first period of the mesozoic era. * triassic jurassic cretaceous permian 21. this was the era of "ancient" life and was divided into six periods. * precambrian paleozoic mesozoic cenozoic 22. which era spans the least amount of time on the geologic time scale? * precambrian paleozoic mesozoic cenozoic

1- Option (C)

2- Option (A)

3- Option (B)

4- Option (D)

Explanation:

By the end of Permian, about 251 million years ago, a huge mass extinction event has taken place which has wiped out nearly 96% of all life forms that existed on earth. The forest-covered area on earth was destroyed completely which took more than 10 million years to replenish. This was the largest mass extinction event in the earth's geological time and is marked by the Permian-Triassic extinction boundary.

The Triassic is the first period that belongs to the Mesozoic era that started from about 251 million years back and ended by almost 200 million years back. It was the time during which the life outside the marine water started to expand and diversify. By the end of Triassic, another mass extinction occurred due to the rapid and widespread eruptions of volcanoes, which resulted in the emission of a huge amount of gases in the atmosphere that unfortunately led to the decrease in the population of numerous species.

The Paleozoic era of "ancient" life and was split into six different periods starting from Cambrian, Ordovician, Silurian, Devonian, Carboniferous and ending at Permian. A lot of events and the evolution of marine organism has taken place during this era.

The Cenozoic era has the least amount of time and is about 65 million only, which is quite less in comparison to the other two eras. This is the era that started after the removal of dinosaurs from the earth in the Cretaceous-Paleocene mass extinction boundary.

answer: ice crystals in air

the water from the water body or another source of water gets evaporated as water vapor as an effect of heat on water. these water vapor rises in the upper layers of the earth atmosphere under high atmospheric pressure. the atmospheric pressure of these water molecules starts to decrease due to the effect of cold air. the invisible water vapor condenses into visible water droplets and ice crystals.these ice crystals and water droplets being less denser than the surrounding air floats on air as clouds.