The amount of work done in stretching a spring from a stretched length of 10 cm to a stretched length of 20 cm is
| A. |
equal to the work done in stretching it from 20 cm to 30 cm |
| B. |
less than the work done in stretching it from 20 cm to 30 cm |
 |
| C. |
more than the work done in stretching it from 20 cm to 30 cm |
| D. |
equal to the work done in stretching it from 0 to 10 cm. |