下面十个句子，每句中有一处错误。错误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（∧），并在其下面写出改加的词。
删除：把多余的词用斜线（﹨）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。
51. I will never forget the day on that I first came to the beautiful school.
52. I don’t believe the reason which he explained me just now.
53. Gun control is a subject with which Americans have argued for a long time.
54. I will never forget the teacher whom I think has helped me most with my studies.
55. The vacation is worthy making use of to visit the cultural relic.
56. Everyone should be able to do what they can make their country stronger．
57. People thought high of what he had done with the Amber Room.
58. The teacher as well as his students is taking active part in the sports meeting.
59. –Where did you see the visiting head of the German government?
--It was in the hotel that she stayed.
60. The police is searching the forest for the missing boy.