We need to identify the component that is invariably present in a tree. (1) Shadow: A tree only casts a shadow when there is a light source. It doesn’t have a shadow in complete darkness. (2) Leaves: Deciduous trees lose their leaves seasonally. Also, young saplings might not have prominent leaves initially, or some types of ’trees’ (like certain cacti adapted to look like trees) might not have leaves in the typical sense. (3) Fruits: Not all trees bear fruit. Also, trees only bear fruit during specific seasons or after reaching a certain maturity. (4) Roots: Roots are essential for anchoring the tree and absorbing water and nutrients from the soil. A living tree cannot exist without roots. Therefore, roots are the component a tree always has. This matches option (4).