<span>A scientific theory is a well-substantiated explanation of some aspect of the natural world that is acquired through the scientific method and repeatedly tested and confirmed through observation and experimentation.</span>
Answer:
The correct option is <u><em>A. they evolved from land mammals.</em></u>
Explanation:
The process of evolution explains how closely one organism is to another based on their common ancestors. Scientists believe that those organisms which show many similarities in their structures or functions might have evolved from a common ancestor in the past.
As in the above-mentioned question, scientists have observed that cetaceans lack gills and breath air, this is a property of land mammals. The cetaceans have fin bones which are similar to the limb bones. As limb bones are present in land mammals, hence they cetaceans and land mammals might have common ancestors in the past.
The given blank can be filled with a feature resulting from hot volcanic rock.
The geysers refer to the rare characteristics on Earth, only about 1000 of them prevail, and more than half of those are situated in Yellowstone. For a geyser to develop, there must be a source of volcanic heat, enough groundwater, and a geologic plumbing system via which the heated water can escape.
The absconding of water takes place when the groundwater is heated by the hot volcanic rocks. The intensifying steam bubbles push the water above via the fissures in the rock until they overflow from the geyser.
With the absconding of the top layers of the water, the pressure on the hotter waters below diminishes, leading to a violent chain reaction of explosions, which expand the volume of the rising boiling water by up to 1500 times or more.
