Which Italian spirit is infused with herbs and spices and often served as an aperitif?

Amaro is a traditional Italian herbal liqueur that is indeed infused with a variety of herbs, spices, and sometimes flowers or roots. This infusion process gives Amaro its distinctive bitter-sweet flavor profile. It is commonly served as an aperitif, meant to stimulate the appetite before a meal.

Grappa, on the other hand, is a type of brandy made from the pomace (the leftover grape skins, seeds, and stems) after winemaking. It has a high alcohol content and is typically served as a digestif rather than an aperitif.

Limoncello is a sweet lemon liqueur that is primarily consumed in southern Italy, usually served chilled as a digestif, and is not characterized by the complex herbal infusion that defines Amaro.

Frangelico is a hazelnut liqueur with a distinctive flavor, but it does not fit the category of being primarily infused with a broad range of herbs and spices like Amaro does. Thus, Amaro is the correct choice for a spirit widely recognized for its herbal and spiced characteristics, especially as an aperitif.