Questions from 31 to 35 are based on the following passage: Generally, cargo is carried in containers, but sometimes it is still shipped as breakbulk cargo. During the voyage, goods may be stacked on top of or come into violent contact with other goods. And the cargo might be dragged, pushed, rolled, or dropped during unloading, while moving through customs, or in transit to the final destination. Moisture is a constant concern because condensation may develop in the hold of a ship even if it is equipped with air conditioning and a dehumidifier(除湿机). Another aspect of this problem is that cargo may also be unloaded in precipitation, or the foreign port may not have covered storage facilities. Buyers are often familiar with the port systems overseas, so they will often specify packaging requirements. If the buyer does not specify this, be sure the goods are prepared using these guidelines: Pack in p containers, adequately sealed and filled when possible. To provide proper bracing in the container, regardless of size, make sure the weight is evenly distributed. Goods should be palletized when possible containerized. Packages and packing filler should be made of moisture-resistant material. To avoid pilferage, avoid writing contents or brand names on packages. Other safeguards include using straps, seals, and shrink wrapping. Observe any product-specific hazardous materials packing requirements. Normally, air shipments require less heavy packing than ocean shipments, though they should still be adequately protected, especially if they are highly pilferable. Finally, because transportation costs are determined by volume and weight, specially reinforced and lightweight packing materials have been developed for exporting. Packing goods to minimize volume and weight while reinforcing them may save money, as well as ensure that the goods are properly packed.
The packing of cargo delivered by air freight can be（）
A．slighter than that of the freight carried by sea
B．heavier than that of the freight carried by sea
C．more pilferable
D．more protective
