What type of dessert is constructed of alternating layers of ice cream and fruit or syrup served in tall, narrow glasses?

The dessert that is constructed of alternating layers of ice cream and fruit or syrup served in tall, narrow glasses is known as a parfait. This treat typically showcases the visual appeal of its layers, making it not only delicious but also aesthetically pleasing. Parfaits are often made with a base of ice cream or yogurt, combined with various fruits, syrups, and sometimes granola or whipped cream, which adds texture and flavor contrast between the different layers.

Sundaes, while also popular ice cream desserts, usually consist of a scoop of ice cream topped with syrup, nuts, fruits, and whipped cream, but they do not typically involve the layered presentation seen in parfaits. Trifles are layered desserts as well, but they usually feature cake rather than ice cream as a base. Cupcakes, on the other hand, are individual cakes topped with frosting and do not fit the layered, glass-served characteristic associated with parfaits. Therefore, the definition and structure of a parfait make it the correct answer for this question.