• 2022-06-07
    设串S1=‘ABCDEFG’,s2=‘PQRST’,函数CONCAT(X,Y)返回X和Y串的连接串,SUBSTR(S,I,J)返回串S从序号I开始的J个字符组成的字串,LENGTH(S)返回串S的长度,则CONCAT(SUBSTR(S1,2,LENGTH(S2)),SUBSTR(S1,LENGTH(S2),2))的结果串是( ):
    A: BCDEF
    B: BCDEFG
    C: BCPQRST
    D: BCDEFEF