You are given three grids, where each of them is 5 by 5 in size.
Grids have empty cells marked with "▢" and filled cells marked with "X".
Your task is to generate a referring expression that best describes the target grid while distinguishing it from the two other distractor grids.
The first grid is the target grid, and the following two grids are the distractors.

Target grid:

▢ ▢ X ▢ ▢
▢ ▢ X ▢ ▢
▢ X X X ▢
▢ X X X ▢
X X X X X

Distractor grid 1:

▢ X X X ▢
▢ X X X ▢
▢ X X X ▢
▢ X X X ▢
▢ X X X ▢

Distractor grid 2:

▢ ▢ X ▢ ▢
▢ ▢ X ▢ ▢
X X X X X
▢ ▢ X ▢ ▢
▢ ▢ X ▢ ▢

Instruction: Describe the target grid.
Generate the referring expression starting with the tag "Expression: " for the given target grid. Omit any other text.
Expression: The grid with a diagonal line of filled cells from the top-left to the bottom-right corner.
assistant
Expression: The target grid has a unique configuration where the filled cells form a straight horizontal line across the middle row, distinguishing it from both distractor grids where either the top or bottom rows are completely filled, and the final distractor where the top row is empty and the bottom row is fully occupied with filled cells.
assistant