4. Which two statements are true regarding single row functions? (Choose two.)
A. They accept only a single argument.
B. They can be nested only to two levels.
C. Arguments can only be column values or constants.
D. They always return a single result row for every row of a queried table.
E. They can return a data type value different from the one that is referenced.
Answer: DE
答案解析：
A.单行函数可以是含有两个参数，如MONTHS_BETWEEN函数。
B.单行函数可以被多级嵌套，所以B答案错误。
C.参数也可以是变量或者表达式，所以C错误
D.单行函数只返回单一值
E. 返回的数据类型值可以与之前引用的数据类型不同，所以正确。
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