Directions: read the paragraph and answer the question.

the great pullman was whirling onward with such dignity of motion that a glance from the window seemed simply to prove that the plains of texas were pouring eastward. vast flats of green grass, dull-hued spaces of mesquite and cactus, little groups of frame houses, woods of light and tender trees, all were sweeping into the east, sweeping over the horizon, a precipice.

which set of details least the reader determine the setting?
a.
pullman, dignity, motion
b.
groups, horizon, precipice
c.
whirling, dignity, window