Hatchet fish are able to make themselves virtually invisible in the dark zone. describe two specific aspects of their body design that allows this kind of camouflage.

Their flat bodies and silver sides.

Explanation:

Hatchet fish have line of photophores on their silver side that produce light or bioluminescence. This property helps the fish to swim in water where sunlight do not penetrate. By producing their own light with the same intensity as that of the sunlight , the hatchetfish can make themselves invisible to the predators. This is called as counter-illumination. Also the large flat bodies of these fishes keep them hidden from predators.

the answer is; comparing the frequency of collisions with and without the device

this makes the anti-collision system an independent variable and the collisions a dependent variable. if there are fewer collisions with an anti-collision system that without, then it can be stated that the system is a success. essentially, collisions under an anti-collision system are compared with the frequency of collisions by cars with the human drivers.