在选择单引号和双引号时要小心。
Be careful about your choice of single versus double quotation marks, as well.
在该字符串中，您可以使用任意多的单引号和双引号(参见清单4)。
Within in the string, you can use as many single and double quotation marks as you like (see Listing 4).
字母之间的空格并不是必须的，但是可以提高可读性，单引号和双引号可以混用。
The Spaces between literals are not required, but help with readability. Any type of quoting can be used.
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