Uncertainty means that your result may be very random, so you can't trust the first or second or so observation, making several samples critical for accuracy. <span />
The answer is c) electromagnetic sawed in which the vibrations are perpendicular to the motion of the sound
There are longitudinal and transverse. Both types of mechanical waves require a medium, transport energy, and have defined wavelengths, frequencies, and speeds.
Differences are that transverse waves oscillate along a direction perpendicular to the direction of travel (like shaking a rope up and down). Longitudinal waves like oscillations along a spring and sound waves, oscillate back and forth along the direction of travel.
