<u>Answer:</u> "Chemical fossils"evidence supports the notion that sponges are some of the earliest known multicellular animals.
<u>Explanation:</u>
Sponges are multicellular animals, may belong to Ediacarian period likely to be 80 million years ago or earlier. They catered through a complex system of internal channels, by moving seawater.
Sponges are soft-bodied and very rarely protected as fossils, therefore finding evidence of existence is giant task. The key of their existence came to know from abnormal chemicals which is a steroids of a particular type generated sufficiently by them but virtually never by ordinary organisms.
Analysis of long strata sequence found in Oman and researchers have been able to extract these "chemical fossils" from samples spanning tens of millions of years — before, during and after the Ediacarian period.This gave clear evidence that sponges had to have evolved long before the great variety of multicellular organisms proliferated at the dawn of that time.
The basic structure of a steroid differ from other macromolecules such as carbohydrates by having a four ring structure whereas a carbohydrate do not have. A steroid is a group of organic substances which has four rings that are arranged in a certain configuration. Examples are testosterone, estradiol and lipid cholesterol. It will always have seventeen carbon atoms in its structure. Carbohydrates, on the other hand, are a group of organic substances that consist carbon, hydrogen and oxygen atoms typically in a 2:1 ratio of the hydrogen and oxygen atoms. So, it would have an empirical formula of Cx(H2O)y.
Ocean currents can be generated by wind so I believe the answer is B
Icthyology would be characterized by the fact that it has to do with fish.
