主句:There are countless others
定从:who simply forget to pay for what they take from the shop.修饰others .
其中:what they take from the shop是宾从作介词for 的宾语.
原因状语:because of age,sickness or plain absent-mindedness
句意:有数不胜数的其他人,由于年龄,疾病和完全的心不在焉而忘记为他们从商店拿的东西付钱.