Concept:
The spring force provides centripetal force.
If natural length is \(l\) and extension is \(x\), then radius of circular path is:
\[
r=l+x
\]
Also,
\[
kx = m\omega^2 r
\]
ip
Step 1: Write the given values.
\[
m=100\text{ g}=0.1\text{ kg}
\]
\[
k=8\text{ N/m}
\]
\[
\omega=8\text{ rad/s}
\]
ip
Step 2: Apply centripetal force condition.
\[
kx = m\omega^2(l+x)
\]
Substitute values:
\[
8x = 0.1\times 64 (l+x)
\]
\[
8x = 6.4(l+x)
\]
\[
8x = 6.4l + 6.4x
\]
\[
1.6x = 6.4l
\]
\[
x=4l
\]
ip
Step 3: Find the ratio of extension to natural length.
\[
x:l = 4:1
\]
ip
Hence, the correct answer is:
\[
\boxed{(D)\ 4:1}
\]