1.The fog is not permanent it moves it stays only for a moment as in the last sentence it moves on.
2. D a metaphor it using the cat as a metaphor for the fog.
The appositive is usually a group of words related to a noun, usually a subject, and describes it in more detail.
The appositive here is a river that flows through Egypt.
Another way of easily spotting an appositive is by looking for commas - if it is separated from the rest of the sentence by commas, it is likely to be an appositive.
The sentence fragment present in those sentences is...
Regina and her younger sisters.
