The correct answer is option 2: loss of all leaves. When a tree loses all of its leaves, it is referred to as defoliation. This can occur due to factors like pests, disease, or extreme weather conditions. Losing all of its leaves can have a significant impact on a tree`s health and overall functionality. Leaves play a crucial role in photosynthesis, which is the process through which trees convert sunlight into energy. When a tree is defoliated, it is unable to produce enough energy to support its growth and other essential functions. Additionally, leaves also provide shade, help regulate temperature, and contribute to moisture retention. Therefore, the loss of all leaves can severely harm a tree by depriving it of vital resources.