$1.2007^{2007}$ 's last digit is ( ).
(A) 1
(B) 3
(C) 7
(D) 9
$-1 . B$.
When $k=1,2, \cdots$, the last digit of $2007^{k}$ cycles through $7,9,3,1$. Since 2007 is a number of the form $4 n+3$, the last digit of $2007^{200}$ is 3.