29. __________ an estimated one million women and men having received plastic surgery.
(A) There are
(B) It is
(C) Approximately
(D) That

“an estimated“是一个固定的短语，表示数量上的估计，意思就是”大约为，估计为“……

an estimated is just a modifier to indicate the 2 million people is not exact, so the verb form would be plural. (approximately 2 million people are)

E.g. Every year an estimated five million children under the age of five die of nutrition -related causes

這是典型的 存在句（there is / there are），意思是「某地／某時有什麼東西／人存在」。

There are an estimated one million women and men having received plastic surgery.
（有大約一百萬名男女曾接受整形手術。）————————————————————

如果想讓句子以 "It is" 開頭，那就需要改寫整個結構，例如：