Ocean waves can cut imposing cliffs along coastlines. A: immobile B: impermeable C: impressive D: imaginative

Floors and walls must be specially constructed to make a building soundproof. A: solid and sturdy B: officially complete C: impermeable to noise. D: architecturally attractive

The inner layer of the exoskeleton (外骨骼) of an arthropod is called the ________. It contains chitin (几丁质), and its outer region is hardened. The outermost layer of the exoskeleton is waxy and impermeable to water. A: epicuticle (上表皮) B: procuticle (原表皮) C: hypodermis (真皮) D: basement membrane (基膜)