Final answer:
Common goods carried by air carriers include electronics, pharmaceuticals, and fresh produce, while heavy machinery is generally not due to its size and weight. The correct option is d.
Step-by-step explanation:
The goods most commonly carried by air carriers are electronics, pharmaceuticals, and fresh produce. These items are often valuable, time-sensitive, and sometimes perishable, which justifies the higher cost of air transport compared to other methods such as shipping by sea or land.
On the other hand, heavy machinery is typically not transported by air due to its large size and weight, making it more cost-effective to ship via sea or land freight. Air freight is better suited to smaller, lighter items that have a high value or require quick delivery. The correct option is d.