What organelle forms spindle fibers during cell division and is exclusive to animal cells?

The centriole is the correct answer because it plays a crucial role in cell division, particularly in the formation of spindle fibers, which are essential for separating chromosomes during mitosis and meiosis. Centrioles are cylindrical structures made up of microtubules, and they are typically found in pairs within a cell. During cell division, centrioles replicate and organize the microtubules to form the spindle apparatus that ensures accurate chromosome segregation.

In contrast, the central vacuole is primarily involved in storage and maintaining turgor pressure in plant cells. Chloroplasts are organelles responsible for photosynthesis in plant cells, and lysosomes contain digestive enzymes for breaking down waste materials, which are also not involved in spindle fiber formation. Thus, centrioles are specifically characteristic to animal cells in the context of spindle fiber formation during cell division.