Joe and I decided to take the long trip we'd always wanted across the country.We were like young kids buying our camper and stocking it with all the necessities of life.Bella bakes the best rhubarb pie.We started out in early spring from Minneapolis and headed west across the northern part of the country.We both enjoyed those people we met at the trailer park.Joe received a watch at his retirement dinner.To our surprise,we found that we liked the warm southern regions very much,and so we decided to stay here in New Mexico.
本段的主题句是段首句,controlling idea（中心思想）是take the long trip across the country.文中出现两个irrelevant sentences,一个是Bella bakes the best rhubarb pie,这一段是讲的是Joe and I ,中间出现一个Bella是不合适的.还有,Joe received a watch at his retirement dinner这一句更是与主题句不相关.再看一个例子：