Question

Thoreau included the following sentence in Walden:

"There is some of the same fitness in a man's building his own house that there is in a bird's building its own nest."

Which of the following statements rephrases his literal comparison as a metaphor?

A man building his house is like a bird building his nest.
A man's house is his nest.
Every bird is an architect and builder of a nest.
Between a human house and an avian nest, there is absolutely no difference in architectural skill.