Phylum is a principal taxonomic category that is ranked below the kingdom and above the class. If two organisms are in the same phylum, this means that they are also in the same kingdom. Each phylum is composed of one or more classes.
The answer is D). Fighting disease
A change in the color of a substance -- this one is indeed a chemical change. Think of iron, if iron turns reddish, it's a completely different substance.
Flatworms-In the life cycle of trematode flukes of the subclass Digenea, mollusks (mostly snails) serve as the intermediate host. Fertilized eggs usually hatch in water. The first larval stage, the miracidium, generally is free-swimming and penetrates a freshwater or marine snail, unless it has already been ingested by one.
Roundworms-Roundworms can complete their life cycle in immature dogs, but as the pup's immune system matures (usually by 6 months of age), the larval stages of the roundworm will become arrested and will encyst (become enclosed in a cyst) in the pup's muscles. They can remain encysted in the dog's tissues for months or years.
