The first known single-celled organisms appeared on Earth about 3.5 billion years ago, roughly a billion years after Earth formed. More complex forms of life took longer to evolve, with the first multicellular animals not appearing until about 600 million years ago.
I think its D but I'm not sure
<span>In the closed awareness context, patients do not know if they are going to die because the doctor and staff deliberately keep the information from them."</span>
B. Roundworms<span>.
The Protostome organisms are subclustered into three main groups,
moreover nematoda or roundworms belongs to the Ecdysozoa group.</span>
<span>Roundworms are organisms that are diverse and almost in clustered to many other ecosystems and environment.
These
Protostome includes mollusks, annelids, and arthropods
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Answer:
Vertebrates are further classified according to several criteria like exoskeleton, respiratory organs, method of giving birth, number of chambers in heart, mode of living etc. They are further classified into classes Pisces, Amphibia, Reptilia, Aves and Mammals
