The beetles gland stores enough hydroquinone and hydrogen peroxide to allow the beetle to release its chemical spray roughly 20 times. Thus pulsed mechanism is beneficial for the beetle survival because the system uses pressure instead of muscles to eject the spray at a constant velocity, saving the beetle energy.
A does not make since because a rock cant have evolved from the trilobite. it is not C because they are extinct. and D was confusing but i chose b whitch was correct