Answer:
Option B,C
Explanation:

Number of nodes =6
From the given equation , we can see that
k=\frac{2\pi}{\lambda}=62.8 m^{-1}
\therefore \lambda=\frac{2\pi}{62.8}m=0.1m
l=\frac{5\lambda}{2}m=0.25m
The mid point of the string is P ,an antinode
\therefore maximum displacement=0.01 m
\omega = 2\pi f=628 s^{-1}
\therefore f=\frac{628}{2\pi}=100 Hz
But this si fifth harmonic freequency .
\therefore Fundamental frequency f0
=\frac{f}{5}=20 Hz