Which of the following are essential elements of a tree’s structure?

The correct choice identifies the fundamental components of a tree's structure. Roots anchor the tree in the soil and absorb water and nutrients, while the trunk serves as the main support system, allowing the tree to grow tall and access sunlight. Branches extend from the trunk and provide further support for leaves, which are vital for photosynthesis — the process through which trees convert sunlight into energy. Each of these parts plays a crucial role in the tree's overall health and functionality, making them essential elements.

Other choices include components that are important to a tree’s reproductive cycle or external protection, but they do not encompass the basic structural elements that are necessary for the tree's growth and stability. For example, flowers and seeds are related to reproduction, while bark serves to protect the tree but is not considered a primary structural element in the same way the trunk and branches are.