\begin{tabular}{l}
Column-I & Column-II \\
\hline I. If $a, b, c$ are in A.P., $b, c, d$ are in G.P. and $c, d, e$ are in H.P., then (A) A.P. \\
$\qquad a, c, e$ are in \\
II. If $2(y-a)$ is the H.M. between $y-x, y-z$ then $x-a, y-a, z-a$ & (B) G.P. \\
are in \\
III. If three numbers are in H.P., then the numbers obtained by subtract- (C) H.P. \\
ing half of the middle number from each of them are in \\
IV. If $a, b, c$ are in G.P., then the equations $a x^{2}+2 b x+c=0$ and $d x^{2}+$ (D) A.G.P. \\
$2 e x+f=0$ have a common root, if $\frac{d}{a}, \frac{e}{b}$ and $\frac{f}{c}$ are in
\end{tabular}