Demand comes mainly from two sources: independent mom-and-pop grocery stores,which, unlike large retail chains are too small to buy straight from producers and food service operators that cater to consumers when they don't eat at home.
    【分析】多重復合句。句子主干為 Demand comes mainly from two sources。冒號后的部分列舉 twosources：一是 independent mom-and-pop grocery stores，二是 food service operators，兩者分別由 which 和 that 引導的定語從句修飾。which 從句中使用了too...to“太...以至于不能”句型，作比較狀語，that 從句中又包含一個 when 引導的時間狀語從句。
    【譯文】需求主要來自兩個方面：一是獨立經(jīng)營的夫妻雜貨店，它們不同于大型零售連鎖店，這種夫妻店因規(guī)模太小無法從生產(chǎn)商那里直購;二是向在外就餐的顧客提供飲食服務的經(jīng)營機構。
    【點撥】1)mom-and-pop“夫妻經(jīng)營的”。2)cater to“迎合;款待;供應伙食”，結(jié)合語境，本句中是“供應伙食”的意思。
    【臨摹】大學應該考慮開設迎合學生興趣和需要的課程。