prep

94.
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A company plans to assign identification numbers to its employees.  Each number is to consist of four different digits from 0 to 9, inclusive, except that the first digit cannot be 0.  How many different identification numbers are possible?

(A) 3,024

(B) 4,536

(C) 5,040

(D) 9,000

(E) 10,000

 答案是B

不好意思,都是些不懂的题目,都没有什么思路,麻烦大家帮帮忙

不好意思,都是些不懂的题目,都没有什么思路,麻烦大家帮帮忙