as

[mengta]

Everyone has given the children up as long dead.

Should I put in " they have been" after "as" in the sentence?

thanks

[Casiopea]

'as' has more than one function:

[1] Everyone has given the children up as long dead.
=> The underlined portion functions as an object complement. It complements or tells us more about the object 'children'. Like this,

. . . the children . . . are long dead.

[2] Everyone has given the children up as they have been long dead.
=> The underlined portion functions adverbially. It tells us why everyone has given up on the children. Like this,

Everyone has given the children up/given up on the children because they have been long dead.