6. The interval that $\sqrt{87654321}$ lies in is ( ).
(A) $[900,1000]$
(B) $[9000,10000]$
(C) $[90000,100000]$
(D) $[2000,3000]$
(E) $[20000,30000]$
$\begin{array}{l}\text { 6. B. } \\ 81000000<87654321<100000000 \text {. }\end{array}$