A.
空串是由空格构成的串 Empty string is a string consisting of spaces.
B.
模式匹配是串的一种重要运算 Pattern matching is an important operation.
C.
串是字符的有限序列 String is a finite sequence of characters.
D.
串是一种数据对象和操作都特殊的线性表 String is a linear list whose data objects and operations both special