Which of the following is a type of petit four sec?

Petit four sec refers to small, dry pastries that are often served as snacks or desserts. The term "sec," meaning "dry" in French, indicates that these pastries do not have a moist filling or components. The most common examples include small cookies, which are baked until crisp and can come in various flavors and forms, making them suitable for serving alongside coffee or tea.

Small cookies fit perfectly within this category as they are typically dry, easy to handle, and can be presented in an appealing manner, often decorated or made with different textures and flavors. They are designed to be bite-sized and are perfect for serving at gatherings or events.

The other options present moist or textured items that do not align with the definition of petit four sec. Pastry cream is a custard used as a filling, making it moist rather than dry. A fruit tart consists of a crust with moist filling and fruits, definitely not dry. A layer cake is made up of multiple moist layers separated by fillings like frosting or cream, further not fitting the "dry" criteria. Thus, the small cookie stands out as the correct option because it embodies the characteristics of a petit four sec, making it a fitting representation of this class of pastries.