git subtree to add the files directly under root folder

Question

I want to add a source repo B into a target repo A directly under the parent folder 'application' of A by using:

git subtree add --prefix=application <remote name of B> <branch name of B>

while being at the parent folder of A.

By doing the above, the result is to create a folder 'application' under the parent folder 'application'. What I want is not to create any child folder, just to append everything under parent folder. I have tried anything like --prefix, --prefix=./ Nothing works. Is there a way to do that?