题目

假定英语课上老师要求同桌之间交换修改作文，请你修改你同桌写的以下作文。文中共有10处语言错误，每句中最多有两处错误仅涉及一个单词的增加、删除或修改。增加：在缺词处加一个漏字符号(^)，并在其下面写出该加的词；删除：把多余的词用(\)划掉；修改：在错的词下画一横线，并在该词下面写出修改后的词。Today we had thehonor of inviting Professor Boucher, foreign teacher from Beijing University,to give us an English lesson. All of us were deep impressed by theunforgettable Engli如图，直线AB与⊙O相切于点A，⊙O的半径为2，若∠OBA=30°，则OB的长为（ ）A．B．4C．D．2