Which of the following is true about using air carriers as a transportation mode when shipping products?
a. Air carriers are the most cost-effective way to ship non-perishable goods over short distances.
b. Air carriers are the slowest and least reliable modes of transport.
c. Air carriers provide in-transit services such as the processing of goods en route.
d. Air carriers are ideal when time is short and speed is needed.
e. Air carriers are a specialized means of shipping chemicals from sources to markets.