Here's why:

* Starch grains are microscopic structures found inside plant cells. They are essentially storage units for carbohydrates (specifically starch).

* Tracheal cells are specialized plant cells that make up the xylem, the tissue responsible for transporting water and nutrients throughout the plant. Tracheal cells are elongated and hollow, forming long tubes that connect the roots to the leaves.

Think of it this way: a starch grain is like a single grain of sand, while a tracheal cell is like a long, thin straw.

Therefore, a starch grain is much smaller than a tracheal cell.