注意这句话的逻辑意思:sound can prevent it's energy from dissipating because there are boundaries in the ocean
not the boundaries causes the energy to dissipating 也就是说应该是boundaries prevent sound's acoustic energy from dissipating 能量应该自己就可以消散。所以dissipate 用主动。by是和prevented一起构成被动。
Sound can travel through water for enormous distances, prevented from dissipating its acoustic energy by boundaries in the ocean created by water layers of differing temperatures and densities.
那么应该选C了?
C.its acoustic energy prevented from dissipating by