Question

Which of the following from To Build a Fire is an effective use of juxtaposition?

"He would be in to camp by six o'clock..."

"The man held steadily on. He was not much given to thinking,"

"He knew that at fifty below spittle crackled on the snow, but this spittle had crackled in the air."

"He had felt the give under his feet and heard the crackle of a snow-hidden ice-skin."