Read the following paragraph from John Muir's "The Calypso Borealis." The rarest and most beautiful of the flowering plants I discovered on this first grand excursion was Calypso borealis (the Hider of the North). I had been fording streams more and more difficult to cross and wading bogs and swamps that seemed more and more extensive and more difficult to force one's way through. Entering one of these great tamarac and arbor-vitae swamps one morning, holding a general though very crooked course by compass, struggling through tangled drooping branches and over and under broad
heaps of fallen trees, I began to fear that I would not be able to reach dry ground before dark, and
therefore would have to pass the night in the swamp and began, faint and hungry, to plan a nest of branches on one of the largest trees or windfalls like a monkey's nest, or eagle's, or Indian's in the flooded forests of the Orinoco described by Humboldt.

Which sentence provides the best summary for this paragraph?

During a very challenging trip, Muir finds a rare plant.

Muir takes a short walk through the woods and makes a profound discovery.

Muir fears for his life yet is forever celebrated for his discovery of the Calypso borealis.

Muir endures the harsh surroundings by spending the night in a cave.