我觉得你老师的讲解有问题，哪有天天拿一个句子的名词性结构老是按照sb/sth去区别讲呢？
楼主想想，万一说话人采用拟人写法，把sth当做sb去看的话，那句子结构该怎么办呢？
这种观念是要不得的，建议楼主要取其精华，去其糟粕。

prove的基本用法如下：
1. Vt. 考验/试验
如：She decided to prove his honesty. 她决定考验他的诚实。
2. Vt. 证明/证实
常用结构如下：
1）prove sth (to sb)
如：Can you prove your theory to us?
2) prove + that从句
How did you prove that he was the robber?
3) prove sb/sth (to be) + n./adj.
The fingerprints on the knife proved him (to be) the murderer.
3. vt/vi. 结果是；被发现是；表现出（自己）是
结构：prove (oneself) + (to be) + n./adj.
The weather forecast proved (to be) accurate on the next day.
She proved (herself) (to be) an able secretary.

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