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【单选题】
“bridge out” wouldactually mean “Meet me.” 40 However, it is also hard to keep a code booksecret for long. So codes must be changed frequently.A.
It is very hard to break a code without the code book.
B.
In any language, some letters are used more than others.
C.
Only people who know the keyword can read the message.
D.
As long as there have been codes, people have tried to break them.
G.
You can hide a message by having the first letters of each word spell it out. F. With a code book, you might write down words that would stand for other words. G. Another way to hide a message is to use symbols to stand for specific letters of the alphabet.F. G.
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【单选题】影响热塑性塑料收缩性的因素很多,下面结论错误的是( )。
A.
模具温度高，熔料冷却慢，收缩大
B.
塑件的形状复杂、壁薄、有嵌件，收缩率小。反之，塑件简单、壁厚、无嵌件，则收缩率大
C.
在同一塑件的不同部位，其收缩率是一样的
D.
塑料品种不同，其收缩率也各不相同
【简答题】方法是一种仅有方法头,没有具体方法体和操作实现的方法,该方法必须在抽象类之中定义。
【简答题】______方法是一种仅有方法头，没有具体方法体和操作实现的方法，该方法必须在抽象类之中定义。______方法是不能被当前类的子类重新定义的方法。
【简答题】方法是一种仅有方法头，没有具体方法体和操作实现的方法。
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