i. At dusk, I allowed Adele to put away books and work, and to run downstairs.
ii. Twilight and snowflakes together thickened the air hid the very shrubs
iii. The afternoon was wild and snowy and we passed it in the schoolroom.
iv. Left alone, I walked to the window but nothing was to be seen there.

Since statement III starts with a general statement about the afternoon weather, it is the aptest starting line of the paragraph.

Statement I follows up III by stating what happened at dusk(after an afternoon), where Adele was allowed to run downstairs. Now, since statement IV describes the scene after Adele left the room, the order of the statements will be III, I, IV, and II.

Thus, the correct option is B.