为了测量一个值，需要进行若干次同样的测量，并取平均值，这是为了消除（）。
A.系统误差
B.工具误差
C.方法误差
D.随机误差
参考答案：D
谁在1886年获得了用汽油机驱动的三轮汽车的专利。
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．length
B．pair
C．size
D．space
