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．每处错误及其修改均仅限一词；
2．只允许修改10处，多者（从第11处起）不计分。
Patsy Smith has raised ducks for many years. One of her ducks, Peg, losing one of his legs in a fight with a tortoise. Mrs. Smith called for help to see whether anyone could create new leg for him. Three students thought it probably to use their 3D printer to print a leg for the poor duck. They spent several months creating and testing different model. It turns out to be a lot more difficult than they had thought! Luckily, their hard work was paid off and they created a model who fitted Peg's leg perfectly. Now, Peg can walk or even run just like her duck partners! Moreover, Mrs. Smith is very thankful for them.
