Question

高二英语

When he was seeing the boring film ，he was very disappointing
为什么不是 disappointed？

Answer 1

我可以很负责任的告诉你,答案就是disappointed.
老师讲的不一定都对, 卷子答案有时候也会出错.

简单的说,
disappointed 是形容因为某人因为某事而失意，沮丧, 主语基本上是人（或有时候拟人手法也会有其它事物) He was disappointed by the disappointing result.

disappointing 所指主语, 本身具体令人失意,沮丧的特征,它不能作为进行时用,因为不是连续动词.
但可做形容词,比如disappointing result,指这个result本身就具体这个让人失望的特征.

举例说the result was disappointing.
the result 就类似" the boring film", 前面半句是一个因,后面是一个后,主语"He"是被这件事搞得失意.

excited, exciting也是这个道理,举个例子:
When he heard the exciting news, he was excited.