The answer is that they do not live on or in the body of a host.
Water makes up 90% of the body.
The factors that affect personal health that are the most easily controlled are c) lifestyle.
You can easily change the way you are living, whereas these other things cannot be.
The answer is RNA polymerase binds to a promoter region of DNA.
I think the hydra lacks the specialized cells for touch and chemical detection. On the other hand earthworms have touch, light, vibration and chemical receptors along the entire body surface. Both of them are invertebrates (those animals without a backbone), they include insects, worms, jelly fish, spiders among other animals.
