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。

注意：1）每处错误及其修改均仅限一词；

2）只允许修改5处，多者（从第6处起）不计分。

Dear Tom,

    I'm glad to know you are crazy about traditional Chinese medical science but eager to study it following an expert. I'd like to recommend Mr. Zhang like your teacher. Mr. Zhang is professor in this field. He often gives medical care to people who have healthy problems. So you can turn to him and to learn medical knowledge from him.

Yours,

Lily

读图，回答下列问题。

在下面列举的各个实例中，哪些情况机械能是守恒的？（   ）