adverb clause

1.
You have such many dresses that it must cost a lot of money.

such後面一定要是a/an+(adjective) noun的嗎？
Ans. Yes, if the noun is singular and countable.

如果物品是眾數，是不是不用ａ／ａｎ？
Ans. You are right.

2.
They are such beautiful girls that a lot of boys invited them to the prom.

如果是ｔｈｅｙ，是不是不用ａ／ａｎ？
Ans. such 後面有冇 a / an 跟句子用咩字開頭無關，完全決定於 such 後的名詞是否 singular and countable。

You have ten dresses.It (They) must cost a lot of money.
You have ten dresses, which must cost a lot of money.

2.That (those) two girls were so beautiful that a lot of boys invited them to the prom.
答案
Those two girls were so beautiful that many boys invited them to the prom.
They were so beautiful that many boys invited them to the prom.

如果物品是眾數，是不是不用ａ／ａｎ？ yes, no A or AN
The dresses cost a lot of money.
They cost a lot of money


adverb clause中such後面一定要是a/an+(adjective) noun的嗎？ NO
如果是ｔｈｅｙ，是不是不用ａ／ａｎ？ YES

They are our classmates.
They are the girls ,we are talking about, whom are invited to the prom.