Final answer:
The Italian meringue is the most stable and dense type due to its preparation method, which involves beating hot sugar syrup into stiff egg whites, cooking the mixture and making it more stable than other forms.
Step-by-step explanation:
The most stable and dense meringue among the options given is c) Italian meringue. Italian meringue is made by gradually beating hot sugar syrup into stiffly beaten egg whites until the mixture cools and becomes very dense and glossy. This method cooks the egg whites, making them more stable than the French meringue which is made from raw beaten egg whites and sugar, and the Swiss meringue which is prepared by gently cooking the egg whites and sugar over a bain-marie before whipping into a foam.
Spanish meringue isn't commonly classified among the main types of meringue, so it could be a typographical error or a less familiar term for a variation of one of the other meringues mentioned. For the most part, Italian meringue is preferred when a more stable structure is needed, such as in buttercream frostings, mousse, and meringue toppings requiring refrigeration or for creations that need to hold their shape for an extended period.