External hard disks can be purchased alone and then attached to the microcomputer with cables; they are used for backing up large amounts of data or for additional storage capacity. 内部硬盘永久性地安置在微机内，只有需维修或更换时才取出。外部硬盘可以独立购买，通过电缆线与微机相连。
The body cannot tolerate such large amounts of radiation. 身体经不住那么大剂量的放射线。
One of the main disadvantages of this system is that it uses very large amounts of fuel. 该系统的主要弱点之一是消耗大量燃料。
