Which order of harmonics is missing or absent in case of stationary sound waves produced in a closed pipe?

The vibrations of four air columns under identical conditions are represented in the figure below. The ratio of frequencies $n_p: n_q: n_r: n_s$ will be

In fundamental mode,the time required for the sound wave to reach up to the closed end of a pipe filled with air is $t$ seconds. The frequency of vibration of the air column is

In a closed-end pipe of length $105 \, cm$,standing waves are set up corresponding to the third overtone. What distance from the closed end,amongst the following,is a pressure node in $cm$?

In an organ pipe whose one end is at $x = 0$,the pressure is expressed by $p = p_0 \cos \frac{3\pi x}{2} \sin 300\pi t$,where $x$ is in meters and $t$ is in seconds. The organ pipe can be:

$A$ closed organ pipe of length $L$ and an open organ pipe contain gases of densities $\rho_1$ and $\rho_2$ respectively. The compressibility of the gases is equal in both the pipes. If the frequencies of their first overtones are the same,then the length of the open organ pipe is: