问题
单项选择题
A four-character password consists of one letter of the alphabet and three different digits between 0 and 9, inclusive. The letter must appear as the second or third character of the password. How many different passwords are possible ？（）
A.5，040
B.18，720
C.26，000
D.37，440
E.52，000
答案
参考答案：D