The correct option is D The number of workers and the time taken to complete the work.
a) As the number of chocolates increases, the cost of chocolates also increases. Hence, direct variation.
b) As the speed increases, distance travelled also increases. Hence it is also an example of direct variation.
c) When the weight of salt increases, the cost of the salt also increases. Hence, direct variation.
d) When the number of workers increases, the time required to do a certain amount of work decreases. Hence, inverse variation.