单项选择题

As I left home after breakfast, I trembled. I was gloomy at the thought that for me this Sunday morning was not the reading of the Sunday papers to cups of tea. I had to sell ice-cream in winter because I had to pay the school fees which was due next month.
The first day was long and lonely. I had to learn to manage my heavy vehicle — the ice-cream cabinet was at the back -- on the icy roads and at the same time try to remember my route and stopping places. Until the late afternoon I had very few customers.
During the next two weeks I was twice caught in heavy snowstorms; in both cases in late afternoon when dusk was falling. The first time, fortunately, I had with me an experienced senior inspector who showed me how to get up a hill in deep snow. He skillfully drove the vehicle to an acute angle to the pavement and used the angle for the rear wheels to push against. We gradually went up the hill — even if rather hard.
The second time I found myself stuck in a valley from which all roads led steeply, and I finished up with the vehicle at an angle on the wrong side of the road. Trying my "angle-pushing" method of hill climbing, I heard a faint tapping on the closed window on the side — the normal serving side. I went across and opened the window. A voice said firmly: "Four six-penny ices, please." I stared in surprise. A queue extended backwards across the road, its tail lost to view in the driving snow. My customers, adults as well as children, had seen me from their houses and had come out, still in sweaters and slippers, with no extra protection against the snow. That afternoon I did more trade stuck there than when I stopped at the proper stopping places.
A former driver, one of my customers, told me another sales theory in bad weather. He said rain or snow kept them from their usual Sunday afternoon walk to their nearest shop; ice-cream available outside homes was an admirable and easy substitute.
Most likely the chief reason why people were eager to buy ice-cream from the author in a snowstorm was that ______.