In context, which is the best version of the underlined portion of sentence 15 (reprinted below) ?

She outlived her husband by several years and is buried at Mount Vernon, which her husband is also buried at.

Vernon, the place which her husband is buried.

Vernon, what her husband was also buried.

Vernon, her husband is buried also.

Vernon, where her husband is also buried.

Vernon, in which her husband is also buried.

Vernon, where her husband is also buried.

Explanation:

The first answer makes it seem like she's still alive.

The second one is just confusing and incorrectly using the word what.

The Third one makes it seem like Vernon is the name of her husband.

The fourth one is correct cause it makes it seem like she died after her husband and he is buried there too.

The fifth one makes it seem like her husband died after her and she was already there.