Dependent demand is the requirement for stock item which is directly related to and therefore de-pendent upon the rate of production (examples are: raw materials, components, energy).
Independent demand is the requirement for stock item which is not directly related to, and is therefore independent of rate of production.
'Number of independent demand items may be derived from the forecast': Although independent demand is called thus, it can still be influenced by economic factors external to the demand-supply model such as general consumer sentiment and consumers' available disposal income. However, businesses that need to predict the number of products with independent demand needed to sate their customers have it easier than businesses that must calculate the demand for products with dependent demand because there are fewer factors to consider.
'Dependent demand items are not directly correlated with production rate': As mentioned above, dependent demand items are directly correlated with production rate.
'All indirect supplies are independent demand items': Though most indirect supplier are inde-pendent demand, some are determined by the production rate, i.e. energy consumption of a major machinery.
'Car engine is an example of independent demand items in a car assembly plant': Car engine is a component in car which is the finished good of a car assembly plant, it is a dependent demand item.
LO 2, AC 2.1

Opening stock is the starting amount of inventory that a business has at a fixed moment in time. This could be the start of a financial year, another reporting period or ad hoc stocktake. The concept of opening stock mush not be confused with raw materials Closing stock is the inventory held at the end of the period under consideration. Thus, the closing stock of one period is automatically the opening stock for the next.
Work in progress is the stock part-way through a manufacturing process; in the service sectors the term is also used for anything between order and delivery.
Buffer stock (safety stock) is the stock held as a contingency or insurance against disruption or unexpected demand.
LO 2, AC 2.1