Answer:
Over time, many species gradually adapted to a more oxygen-rich enviroment, allowing them to survive in shallow water and on land.
The correct answer is option D, Speciation
In the allopatric speciation, the geographical barriers such as mountains or rivers causes isolation of the population. The two population groups get completely separate from each other and thus develop different sexual preferences for mating.
The answer is a process that selects variation that help survival and that spreads the variation to more offsprings.
The idea is that there is a higher chance of survival if the organisms has certain characteristics and it is more likely to pass on their genes of this characteristic to the next generations.
For example, there's dark colored fish and white fish. In the deep ocean, dark colored fish can camouflage themselves. However, white fish can be seen easily by predators. Therefore, eventually more dark colored fish survives and more offsprings are dark ones.
Evaporation of water from plants:)
Ash can be harmful to an environment. It mostly depends on how much ash there is though. If a volcano erupted such as Mt. St. Helen's then yes that can harm an environment. Ash can cover the sky and block out the sun for days before disappearing and that will affect the life of plants