关于seat现在分词和过去分词的用法

Question

there are ten waiting rooms at the newly-built station ,____in all 20,000 people.
A.seated B. seating 答案选A 这里是说seating现在分词做定语用，也符合逻辑，修饰station嘛。可我查字典说，seated和sitting做定语、状语、宾补。怎么变seating了呢？难道是因为那个逗号？

Ladies and gentleman，please remian ______until the plane has come to a complete stop A.seated B. seating 答案选A 但seated在这个句子里面做什么成分呢？

还有I saw some villagers____on the beach at the end of the room.
A.seated B. seating 答案选B 了 我不知道为什么了。。。。

来请教高手了！

Answer 1

第一句用seated是因为前面有waiting room，这里的seated有被动的含义。
第二句seated是形容词，做联系动词remain的表语。
第三句是see sb. doing sth 的句型，表示看到某人正在做某事。

Answer 2

一般来说sb. be seated in sp.
sb. be sitting in sp.
第一句正常语序为all 20,000 people seated in ten waiting rooms 可容纳20000人入座
第二句remain相当于be动词 可以看作be seated
第三句我认为是being seated

Answer 3

1.seated
2.seated
3.sitting