The correct answer is: A. Ground level
A damp proof course (DPC) is a barrier that is installed in a building to prevent water from rising up through the ground and damaging the structure. It is typically made of a material such as bitumen, plastic, or slate, and is installed at ground level, just above the foundation.
Plinth level is the level of the ground at the base of a wall. It is typically higher than ground level, and is used to protect the wall from moisture and damage.
Water table level is the level at which the ground is saturated with water. It is typically lower than ground level, and can vary depending on the time of year and the amount of rainfall.
Midway ground level and water-table level is not a common location for a DPC. It would not be effective in preventing water from rising up through the ground, as it would be located below the water table.
In conclusion, the correct answer is: A. Ground level.