Identify and shade simple 2D shapes according to color-coded instructions on this educational worksheet.

Problem Description:

The task is to identify and shade simple 2D shapes based on the given instructions. The shapes need to be shaded according to the following rules:

- Squares: Shade in blue.
- Triangles: Shade in green.
- Circles: Shade in red.
- Rectangles: Shade in yellow.
- Other shapes: Leave unshaded (white).

Solution Approach:

1. Identify each shape in the grid.
2. Classify each shape into one of the categories: squares, triangles, circles, rectangles, or other shapes.
3. Shade the shapes according to the specified colors for squares, triangles, circles, and rectangles.
4. Leave other shapes unshaded.

Step-by-Step Solution:

#### Row 1:
1. Shape 1: Rectangle (shade yellow).
2. Shape 2: Pentagon (leave white).
3. Shape 3: Circle (shade red).
4. Shape 4: Triangle (shade green).

#### Row 2:
1. Shape 5: Irregular shape (leave white).
2. Shape 6: Square (shade blue).
3. Shape 7: Hexagon (leave white).
4. Shape 8: Circle (shade red).

#### Row 3:
1. Shape 9: Trapezoid (leave white).
2. Shape 10: Triangle (shade green).
3. Shape 11: Irregular shape (leave white).
4. Shape 12: Rectangle (shade yellow).

#### Row 4:
1. Shape 13: Square (shade blue).
2. Shape 14: Triangle (shade green).
3. Shape 15: Rectangle (shade yellow).
4. Shape 16: Triangle (shade green).

Final Shading Instructions:

- Blue (Squares): Shapes 6, 13.
- Green (Triangles): Shapes 4, 10, 14, 16.
- Red (Circles): Shapes 3, 8.
- Yellow (Rectangles): Shapes 1, 12, 15.
- White (Other shapes): Shapes 2, 5, 7, 9, 11.

Final Answer:

\[
\boxed{
\text{Shade as follows:}
\begin{array}{cccc}
\text{Yellow} & \text{White} & \text{Red} & \text{Green} \\
\text{White} & \text{Blue} & \text{White} & \text{Red} \\
\text{White} & \text{Green} & \text{White} & \text{Yellow} \\
\text{Blue} & \text{Green} & \text{Yellow} & \text{Green}
\end{array}
}
\]