根据短文内容，用方框中所给单词的适当形式填空，每词限用一次。

Some colors make us feel calm and peaceful. Blue is one of these colors. Wearing blue clothes or sleeping in a blue 　小题1:　 is good for the mind and body. Blue can 　小题2:　 mean sadness. Someone who is feeling sad may say “I’m feeling blue.” Some colors make us feel happy. Orange is such a happy color. It can bring you happiness and cheer you up when you are sad. If you feel 　小题3:　 or weak, please wear colors that make you feel energetic. Green can give you energy, because it 　小题4:　 new life. And you can also wear red. That makes it easier 　小题5:　 you to take action.

两个公司希望通过Internet进行安全通信，保证从信息源到目的地之间的数据传输以密文形式出现，而且公司不希望由于在中间节点使用特殊的安全单元增加开支，最合适的加密方式是 (2) ，使用的会话密钥算法应该是 (3) 。

A．RSA

B．RC-5

C．MD5

D．ECC