Velocity in a wave $=\sqrt{\frac{T}{\mu}}$
Fundamental frequency of waves $\frac{v}{2 l}$
$f=\sqrt{\frac{T}{\mu}} \times \frac{1}{2 l} \quad \dots (i)$
If $T$ decreases by $19 \%$ value of $T$ will be $T-0.19 T$
Putting this value in $(i)$
$f^{\prime}=\sqrt{\frac{T}{\mu}} \frac{(1-0.19)^{1 / 2}}{2 l}$
$f^{\prime}=f\left(1-\frac{1}{2} \times 0.19\right)$
[Binomial theorem]
$f^{\prime}=f-0.1 f$
Hence, the frequency decreases by $0.1 f$ are $10 \%$ of initial value.
(image)
[$A$] The time $\mathrm{T}_{A 0}=\mathrm{T}_{\mathrm{OA}}$
[$B$] The velocities of the two pulses (Pulse $1$ and Pulse $2$) are the same at the midpoint of rope.
[$C$] The wavelength of Pulse $1$ becomes longer when it reaches point $A$.
[$D$] The velocity of any pulse along the rope is independent of its frequency and wavelength.