Production is the organized activity of transforming resources into finished products in the form of goods and services; the objective of production is to satisfy the needs of the final consumer. This production involves the identification of human needs, producing goods that have utility to satisfy humans. It doesn't involve when goods are consumed.
The law of diminishing marginal utility states that, as the consumption of a particular commodity increases, the marginal utility/satisfaction gotten from the consumption of an additional unit of the said commodity will fall/decrease.
A change in demand means a shift in consumer desire to purchase a particular good or service, irrespective of a difference in its price. From the options given above, the price of the commodity does not cause a change in demand, option D is therefore correct.
Joint demand is when you need two goods because they work together. If two goods are in joint demand they will have a high and negative cross elasticity of demand. This means a rise in the price of one will lead to a decrease in the demand for the other. Therefore option D is correct. An increase in the price of P, will lead to a decrease in the quantity demanded of Q.
The price mechanism is a mechanism where price plays a key role in directing the activities of producers, consumers, resource suppliers. It aids in resource allocation, as both the buyer and seller can decide on what product to produce and what to buy.
National emergencies are unforeseen events that affect a geographical location, hence leading to a stop or slow down economic activities. An example of such is an outbreak of an epidemic, wars, natural disasters, etc. These emergencies are unpredictable and as such can cause a change in supply.