Answer: B. They seldom think about the dead woman.
In this poem by Thomas Hardy, a woman who is dead and buried notices someone is digging on her grave. She begins to question the person, trying to find out who it is. However, she realizes that no one remembers her, or cares that she is buried in that place. All of the people she knew seldom think about her, or visit the site. In fact, the digger is her dog, who is simply burying a bone and had also forgotten this was the site of her grave.
A foil is a character whose traits are distinct or different from another character. Rainsford's character is highlighted by its difference from Zaroff's character. Zaroof is ruthless and cruel while Rainsford is compassionate and values life. You could say that their characters are the complete opposite.