破译密文的关键是()。A．截获密文 B．截获密文并获得密钥 C．截获密文，获得密钥并
题型：单项选择题
问题：
破译密文的关键是()。
A．截获密文
B．截获密文并获得密钥
C．截获密文，获得密钥并了解解密算法
D．截获密文，了解加密算法和解密算法
题型：单项选择题
根据图片及首字母提示补全下列单词，使短文内容完整、连贯。
Today is Christmas Day. My 
1.h____________ is very beautiful. We have a
big 
2.C____________ tree with a 
3.s____________ on the top.
In the morning, I received (收到) many gifts, and Christmas 
4.c____________.
I was very happy. " Who brought me these gifts, Mum? " I asked. “ 
5.S____________
brought you last night." said Mum. But I don't think so. I think my Mum and Dad brought them.
They love me very much.