Which word in this passage from "the killers in our midst" gives it a more casual style? a."totally" b."rapidly" c."unprovoked" d."angry"?

apex says answer is totally

the invasive species was introduced due to commercial purpouses, as there was a demand for fur clothes and hence, a business opportunity connected to this product. actually, it was when the nutrias scaped, causing harm to the us ecosystems when they acquired the status of invasive species. in this case they have caused an environmental problem, but it could have affected also economic interests or even human health.