谁能帮我解释一下这道题是什么意思？多谢。

if the number 52,1n9, where n represents the tens digit, is a multiple of 3, then the value of n could be which of the following?

a. 6

b.5

c.3

d.1

e.0

答案是D

521n9是3的倍数，n是其十位，n有可能是以下哪个数？