在公钥密码体制中，不公开的是( )。
Ⅰ．公钥
Ⅱ．私钥
Ⅲ．加密算法
A) Ⅰ
B) Ⅱ
C) Ⅰ和Ⅱ
D) Ⅱ和Ⅲ
参考答案：B
解析： 公钥密码体制有两个不同的密钥，它可将加密功能和解密功能分开。一个密钥称为私钥，它被秘密保存；另一个密钥称为公钥，不需要保密。对于公钥加密，Ⅲ算法和公钥都是公开的。所以选项B)正确，私钥不能公开。
Directions: There are 10 blanks in the following passage. For each numbered blank, there are four choices marked A, B, C and D. Choose the best one and mark your answer on the ANSWER SHEET with a single line through the center.
| Our planet is like a bit spaceship. Our atmosphere acts (51) a shield against harmful radiation and space debris. (52) holds the air and people on the spaceship, (53) everything doesn’t float away. Each of us is an astronaut and our spaceship, the earth, provides our food and water. The sun is our energy (54) and without it we would not be able to survive. (55) every spaceship, the earth is a closed system. The only thing we receive from the outside is energy from the sun. Everything else must be used (56) again. We astronauts don’t seem to realize that this spaceship is the (57) one we’ve got. We (58) its resources and waste the energy the plants have stored from the sun. If we (59) our spaceship, we will destroy ourselves as well. Maybe if we look at the universe which surrounds us, we will appreciate our own spaceship more and take (60) care of it. |
A．for
B．with
C．as
D．like