Rank the fossils of organisms a–e from most common to least common. if two fossils have the same commonness, overlap them.

Factors b,d,e,g are favorable to fossil formation and preservation. 
Hard bodies are more easily preserved; rivers and oceans deposit muds that keep bodies intact for long times after death; large population and long existence provide more opportunity for fossils to form; and a low oxygen content impedes decay and inhibits predators. 
Factors a,c,f,h are unfavorable to fossil formation and preservation. 

Thus, Organism E with 4 positive factors is number 1 -- has the top chance of forming a fossil. 
Organism D with 4 negative factors would be number 5 -- has very little chance of forming fossils. 
Of the other 3, all have soft bodies, so are "disadvantaged" compared to E...but 
Organism A has no OTHER disadvantages, so is probably number 2 (second best fossil chance). 
Organism C has ALMOST everything going against it -- despite its large population and long existence, it has no other positive factors -- so I'd put it at number 4 (second worst). 

To summarize, my rankings are 
1. E, 2. A, 3. B, 4. C, 5. D

They create genetic variations