With 1-4. urgent need on physics questions. 100% correct answers

1).  Speed of any wave = (wavelength) x (frequency) .  I got 4.5 m/s in my head, but you need to check this.

2).  and  3).  are marked correctly

4).  Transverse waves have crests and troughs.  But sound waves are longitudinal waves, so they don't have any.  The wavelength of a sound wave is the distance between consecutive centers of compression (or rarefaction).

powerful computers now, not then

vapour or gas assuming atmospheriv pressure