Which of the following trees is commonly called Quaking Aspen?

The tree commonly known as Quaking Aspen is Populus tremuloides. This species is renowned for its distinctive white bark and shimmering leaves that tremble in the breeze, giving it the "quaking" epithet. It is a deciduous tree native to North America and is often found in clusters, forming beautiful stands in both forested and open areas.

The leaves of Populus tremuloides are flat-stemmed, which allows them to flutter in the wind, creating a striking visual effect and a soothing sound, contributing to its common name. This tree is also valued for its rapid growth and ability to thrive in a variety of soil types, making it a popular choice for reforestation and landscaping.

Other trees listed in the choices have different characteristics and belong to different genera. For instance, Pyrus calleryana is known as Callery Pear, while Nyssa sylvatica is commonly referred to as Black Gum, and Quercus coccinea is known as Scarlet Oak. Each of these species has unique features and ecological roles that differentiate them from Populus tremuloides.