Answer
$C \lt B \lt A$
Work Step by Step
We know that Bohr radius is proportional to $-\frac{Z^2}{n^2}$
For atom (A)$-\frac{Z^2}{n^2}=-(\frac{1}{3})^2=-\frac{1}{9}$
For atom (B)$-\frac{Z^2}{n^2}=-(\frac{2}{2})^2=-1$
For atom (C)$-\frac{Z^2}{n^2}=-(\frac{3}{1})^2=-9$
Thus, the increasing order is:
$C \lt B \lt A$
