“which” (L.25) can be correctly replaced by what.

wrong. which could be fittingly replaced by that, however not by what. Both which and that play the role of relative pronouns as they're mainly used to stand in for the element of the main clause. What can't be used to mark a relative clause.

ERRADO.
"The Be Food Safe Campaign, which is grounded in social marketing"

O "which" que funciona como "que" na frase, está restringindo a campanha "The Be Food Safe". Essa campanha é fundamentada (grounded) no marketing social

Which e who só podem ser substituídos por that.