D

Step 1: Understanding the graph
The acceleration $a$ is represented as a function of the position $x$ (in cm). The graph consists of two parts:
- A linear increase from (0, 0) to (6, 20) cm/sec²
- A constant value of 20 cm/sec² from (6, 20) to (8, 20) cm/sec².

Step 2: Finding work done using the area under the curve
Work done $W$ on the mass can be found by calculating the area under the acceleration curve from $x = 0$ to $x = 8$ cm.

Step 3: Calculate area for the triangular part
The first part of the graph forms a triangle:
- Base = 6 cm
- Height = 20 cm/sec²
Area of the triangle $A_{triangle} = \frac{1}{2} \times base \times height = \frac{1}{2} \times 6 \times 20 = 60 ext{ cm/s}^2$

Step 4: Calculate area for the rectangular part
The second part of the graph forms a rectangle:
- Width = 2 cm (from 6 to 8 cm)
- Height = 20 cm/sec²
Area of the rectangle $A_{rectangle} = width \times height = 2 \times 20 = 40 ext{ cm/s}^2$

Step 5: Total work done
Total area under the curve = Area of triangle + Area of rectangle = 60 + 40 = 100 cm/s².

Step 6: Conversion to Joules
To convert this to work done: $W = mass \times area = 10 ext{ kg} \times 100 ext{ cm/s}^2 = 1000 \text{ cm}^2/s^2$ = 10 Joules (since 1 J = 100 cm²/s²).

Therefore, the total work done is 10 Joules.