If you set up the seventh harmonic on a string fixed at both ends,how many nodes and antinodes are set up in it?

In stationary waves,

$A$ rod of length $1.2\,m$ is clamped at the midpoint and its fundamental frequency is $2\,MHz$. What is the speed of the wave inside the rod?

At a certain instant,a stationary transverse wave is found to have maximum kinetic energy. The appearance of the string at that instant is:

Length of a string tied to two rigid supports is $40 \ cm$. The maximum wavelength (in $cm$) of a stationary wave produced on it is ... $cm$.

One end of a taut string of length $3 \ m$ along the $x$-axis is fixed at $x=0$. The speed of the waves in the string is $100 \ m/s$. The other end of the string is vibrating in the $y$-direction so that stationary waves are set up in the string. The possible waveform$(s)$ of these stationary waves is (are):
$(A)$ $y(x,t) = A \sin \frac{\pi x}{6} \cos \frac{50 \pi t}{3}$
$(B)$ $y(x,t) = A \sin \frac{\pi x}{3} \cos \frac{100 \pi t}{3}$
$(C)$ $y(x,t) = A \sin \frac{5 \pi x}{6} \cos \frac{250 \pi t}{3}$
$(D)$ $y(x,t) = A \sin \frac{5 \pi x}{2} \cos 250 \pi t$