a)He believes it is stealthy and all-encompassing.
He describes the fog as being everywhere when he says its on the window-panes, in the drain pools, and "into the corners of the evening". All-encompassing means that it is everywhere, surrounding everything. The way the speaker leaves out any mention of sound or noise makes it seem as though this fog moves quietly. The description of the fog going to the window-panes, the corners, and the pools gives it a quick stealthy feel.
It can be
1+1=2
0+2=2
or some of these kind of pairs.
Hope that this all helps you!=)
Answer
It's important to notice the little things because it connects you to the person more.
Explanation: