Which of the following statements is true regarding long bones?

Long bones are indeed characterized by a shaft with two ends, which is a defining feature of their structure. The shaft, known as the diaphysis, is typically cylindrical and provides strength and support, while the ends, known as epiphyses, are often wider and help to form joints with adjacent bones. This structure allows long bones to support weight and facilitate movement, making them crucial for the overall function of the skeletal system.

In contrast, irregular bones have complex shapes and do not fit into the categories of long, short, or flat bones, while flat bones are generally thin and flattened, serving purposes such as protection and muscle attachment. The presence of air spaces is typically associated with certain types of bones, like those in the skull (e.g., sinuses), rather than long bones, which are generally solid to provide the necessary strength for support and movement. Thus, the identification of long bones as having a shaft with two ends is what makes the statement true.