题目内容：
根据以下材料，回答题In our online life, we need to usepasswords frequently. We usepasswords 21 e-mail,gaming sites, socialnetworking sites, and other shopping sites. 22 , the passwords most people useare not very 23 and can easily be"broken" by others. In fact, the most commonly used passwords are sosimple that it requires very 24 effort to figure them out. Can youguess 25 the most commonly used passwordsare? They are: Names of baseball teams, birth dates of a family 26 , the year of a special sportsevent, the random numbers like 156468, 27 the name of a friend, pet,favorite TV star, or band.
There are programs 28 to break into people's onlineaccounts. These programs are29 of trying everyword in the English dictionary and the dictionaries 30 many foreignlanguages, in their effort to break into an account. 31 can even search words backward. Somewill try 32 words or words that are followedby numbers, 33 school222. These programs can testmillions of passwords in a few minutes. So, you are advised to be carefulabout 34 passwords so that they
will be hard to break. You are also advisednot to make them 35 hard to remember. Meanwhile,you need tochange them once in a while.
第21题答案是 A．to
A．to
B．with
B．with
C．by
C．by
D．for
D．for
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答案解析：