短文改错。
文中共有10处语言错误，每句中最多两处。错误涉及一个单词的增加、删除或修改。
增加：在此处加一个漏词符号（∧），并在其下面写出该加的词。
删除：把多余的词用斜线（＼）划掉。
修改：在错的词下划一横线，并在该词下面写出修改后的词。
注意：1.每处错误及修改均仅限一词；
2.只允许修改10处，多者（从11处起）不计分。
Last week our class has organized an activity to thank our teachers before graduation. In Thursday we
had a class meeting to discuss what to do. We came up many good ideas. Then we decided to send them
gifts and did some good deeds. The next day we carried our plan. Some of us cleaned the teachers' office
and decorated it with pots of flowers, make it more comfortable for the teachers to work. Others helped
wash the cars and bikes. And still others gave well- prepared gifts to the teachers, which were very pleasant
and expressed their best wishes to us.
We all felt happy about how we had done for our teachers.
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游离端可摘局部义齿，
分别为三臂卡环，颊、舌侧基托伸展稍长，基托远中覆盖磨牙后垫前缘。指压时，义齿前后翘动。引起义齿翘动的主要原因是（）.