Bella is designing a model of a longitudinal sound wave for her science classroom. Which of the following pieces of information should Bella include in her model? Choose the two statements that apply.
A. Sound must travel through a material to transfer energy
B. Sound must travel through a vacuum to transfer energy.
C. Rarefaction and compression are properties of longitudinal waves.
D. Crests and troughs are properties of longitudinal waves.

8) animals respond in various ways to stimuli detected through their senses. some of these responses are stimulated by the presence of danger. which of these animal responses is the best example of a response to an immediate threat? a) a rooster crows every morning at the first sign of light. b) as something approaches an octopus, it shoots a cloud of ink. c) from late fall until spring, bears hibernate to preserve energy. d) a dog is getting hot in the sunlight, so he moves to a shaded area.