下列工程计量办法叙述正确的是( )。

A．确定按合同完成的工程数量所采用的量测和计算方法，如在有关部分未做具体规定时，应符合国际公路工程的习惯做法

B．按照合同应计量的所有工程细目，应以分制的物理计量单位或习惯的自然计量单位进行计量

C．一切工程的计量，应由承包人提供符合精度要求的计量设备和条件

D．凡超出了图纸所示或监理工程师指示的长度、面积或体积，均视为已包含在项目单价中，不予计量

E．全部必需的模板、脚手架、装备、机具等材料均应单独计量

In a public-key cryptosystem, (71) encrypted with the public key can only be deciphered with the private key from the same (72) . Conversely, (71) encrypted with the private key can be decrypted only with the public key. Users can make their public keys (73) available or place them at a key distribution center or others to access. However, the private key must be (74) safe. In public-key systems there’s no (75) to find a safe channel for communicating a shared secret key.

A. more B. necessary C. need D. space