Black background in transparant images

Let me 1st explain what is happening.

1/ Place a Photoshop image with transparent background in Illustrator.
2/ Save a 1.5 pdf (or higher).
3/ Open the pdf in Acrobat, select the image, copy it.
4/ Open Photoshop, make new image and past the image you copied b4 from
Acrobat.

You will see that the transparency is filled in with a black color.

Why is this?
And can this be changed, so i can have a whit background?

I don't imagine you will be able to copy and paste an image with
transparency. Maybe using the Object Touch-up Tool in Acrobat Pro to
open the image directly in Acrobat will preserve the transparency, but
not if it was done with a clipping path.

Yes I know, but the question was, why does it make a Black k background instead
of white?

I doubt you can control this. Acrobat is unlikely to have made the
choice, more likely done by Photoshop.

No i am shure its made like this in the pdf file.
As far as i know if you make a pdf file frome a Illustrator file with a linked
Photoshop file, he wil make a pdf file with new images in it but those images
wont be the original Photoshop file.