A
it's the most grammatically correct and understandable
Answer:
Due to presence at early days of the planet.
Explanation:
We only find the remains of single celled organisms in the oldest fossils because the single celled organisms are the organisms that were present in the early days of this planet. These single celled microbes were present about 3.7 billion years ago while on the other hand, the oldest rocks are only a little older i. e. 3.8 billion years so these single celled organisms are considered as oldest fossils on this planet.
Grasshoppers have no ears, instead they use an organ called the tympanum located in the first segment of their abdomen, whereas humans take in sound waves through the ear canal until they reach the eardrum. The eardrum picks up the vibrations and then transmits them to tiny bones in the middle of the ear, the bones pass the vibrations to the inner ear (which is filled with liquid) and the cochlea.
Hope I could help.
<span>Sponges have cellular-level organization, meaning that that their cells are specialized so that different cells perform different functions, but similar cells are not organized into tissues and bodies are a sort of loose aggregation of different kinds of cells. This is the simplest kind of cellular organization found among parazoans.
<em>I hope this helps!~</em><em /></span>
