Amarine biologist dredges up a small animal from the bottom of the ocean. it is uniformly segmented, with short, stiff appendages and soft, flexible skin. it has a complete digestive system and a closed circulatory system, plus multiple true coeloms. based on this, you determine that the animal must be a(n)

First, a complete digestive system means that the digestive tract has a beginning or the oral end and the opposite end or the aboral end. This is found in more complex animals starting from roundworms (flatworms have an incomplete digestive tract). A closed circulatory system is found in animals more recent than mollusks. The presence of the coelom makes it more evolved than the flatworms. 

Specifically, a small animal with a segmented body, short stiff appendages, and soft skin with the above characteristics point out to the phylum Annelida or annelids.

chlorophyll a: this is the most abundant pigment in plants. chlorophyll a absorbs light with wavelengths of 430nm(blue) and 662nm(red). it reflects green light strongly so it appears green to us.

not necessarily. higher fitness requires the organism to be reproductive successful. for example, an organism at age 10 with 15 offspring is much more fit than an organism at age 15 with only 5 offspring.