Ginkgo - Archegonia
Mustard - Synergids
Salvinia - Prothallus
Viroids - RNA
Salvinia is a heterosporous fern where the reproductive structures are born on the fruiting body sporocarps. They either bear microsporangia or megasporangia i.e., monosporangiate. Thus the reproductive structures are not born on prothallus rather on specialized sporocarp. Thus, the correct answer is option A.