英语问题请教，谢谢！

There have been many people missing. [很多人都已经不见了。]
请问这句话里的missing是形容词，还是现在分词？
我从来没见过There have been 后加 ing 形式的，请问为什么要这样用？
there be +主语+-ing的用法是常见的。只不过你的句子是完成时而已。
There are many people swimming in the river.河里有许多人在游泳。可以理解为：people who are swimming

这里的missing是形容词还是现在分词不重要，只要知道它的用法就好了。
要表示某人、某物不见了，常用两个词表示：lose和miss.
用lose时，常用其过去分词形式：
1.　She looked out of the window, sighing for her lost youth.
她看着窗外，为她失去的青春而惋惜。
2. He is hunting for his lost book.
他正在寻找一本丢失的书。
3.　The lost man yelled, hoping someone in the woods could hear him.
迷路的人大声喊叫着,希望林子里有人能听见。

用miss时，常用其现在分词形式：
1. The child had been missing for a week.
那个孩子已经下落不明一个星期了。
2. The book had two pages missing.
那本书缺两页。
3. The hammer is missing from my toolbox.
我的工具箱里少了一把锤子。
4. Police are combing the woods for the missing children.
警察搜遍树林以寻找失踪的孩子。

missing是people的宾语补足语，是个形容词。

missing表示一种状态，记住用法即可

应该是形容词