One category of these entities is referred to as 'mechanical,' since they must travel through a medium. Longitudinal ones travel parallel to the motion of energy, while transverse ones travel at a right angle. Surface ones travel in a circular motion, and electromagnetic ones can travel in a vacuum. For 10 points, name these scientific disturbances that transfer energy through matter or space.
a) Waves
b) Particles
c) Quarks
d) Photons