Answer
We can rank the samples according to their disintegration constant:
$B \gt A= C$
Work Step by Step
In part (a), we ranked the samples according to their half-life:
$A = C \gt B$
We can write an expression for the disintegration constant:
$\lambda = \frac{ln~2}{T_{1/2}}$
As the half-life $T_{1/2}$ increases, the disintegration constant $\lambda$ decreases.
We can rank the samples according to their disintegration constant:
$B \gt A= C$
