Answer:
Option D, When the oil has already started to break down
Explanation:
The manual mode of cleaning an oil spill involves the usage of equipment’s such as hands, rakes, shovels etc.. These equipment’s are hand held tools and thus can be used in places where oil spill has just taken place and it is still at the surface.
In case If the oil spill sunk to the bottom, manual scavenging will not help. Also if the quantity of oil spill is too high, the manual equipment will not produce desirable results.
