题目

阅读理解 Seventy-three-year-old Gary selected his foodin Value Mart more carefully than NASA chose its candidates for the spaceshuttle. Skim milk was $2.99, on sale from $3.49; white bread, 89 cents with adiscount; table salt, 99 cents, 20 cents off the regular price. Leaving thecashier (收银员), he estimated that he hadsaved 80 cents today. He was pleased that he had got good value for his moneyagain. At the exit, the cold wind reminded him of hisgloves. “Now where are they?” Not in the coat pockets. Not in the grocery bageither. The worried man made a thorough search of all his po在图中根据小磁针静止时的指向标出通电螺线管的两极和电源的正负极．