I have two brothers and .[ ]
A. uncle
B. grandmother
C. sisters
答案：C
Usually there is a blackboard on the front wall in the classroom, _________there is a slogan.
A．above which
B．in that
C．on which
D．from that
根据密码分析者所掌握的分析资料的不通，密码分析一般可分为4类：唯密文攻击、已知明文攻击、选择明文攻击、选择密文攻击，其中破译难度最大的是（）。
A、唯密文攻击
B、已知明文攻击
C、选择明文攻击
D、选择密文攻击
