The appositive phrase is not Maya Lin, like the comment above me stated, but it is B) Chinese-American.
An appositive phrase is usually separated from the rest of the sentence by commas, and it describes the subject, which here is Maya Lin.
The plot is always the overriding idea in fiction.
The speaker is talking about the water. During winter, the water enters the cracks and freezes and expands. It breaks the stone and makes cracks and when the water melts the holes are bigger. What he is describing is mechanical weathering which is common in nature.
It is a metaphor because it is comparing one thing to another.
