Question: Answer the following question given this paragraph: Echinoderms lack respiratory and excretory systems. Instead, the thin walls of their tube feet allow oxygen to diffuse in and wastes to diffuse out. Echinoderms also lack a centralized nervous system. They have an open circulatory system and lack a heart. On the other hand, echinoderms have a well-developed coelom and a complete digestive system. Echinoderms use pheromones to communicate with each other. They detect the chemicals with sensory cells on their body surface. Some echinoderms also have simple eyes ( ocelli ) that can sense light. Like annelids, echinoderms have the ability to regenerate a missing body part. Q: Echinoderms lack what type of system that in humans consists of the brain and spinal cord? Choices: - autonomic system - endocrine system - peripheral nervous system - centralized nervous system A:
Answer: centralized nervous system

Question: Answer the following question given this paragraph: As with melting, the energy in boiling goes exclusively to changing the phase of a substance; it does not go into changing the temperature of a substance. So boiling is also an isothermal process. Only when all of a substance has boiled does any additional energy go to changing its temperature. What happens when a liquid becomes a gas? We have already established that a liquid is composed of particles in contact with each other. When a liquid becomes a gas, the particles separate from each other, with each particle going its own way in space. This is how gases tend to fill their containers. Indeed, in the gas phase most of the volume is empty space; only about 1/1,000th of the volume is actually taken up by matter (Figure 10.4 "Liquids and Gases"). It is this property of gases that explains why they can be compressed, a fact that is considered in Chapter 6 "Gases". Figure 10.4 Liquids and Gases. Q: What kind of process is boiling? Choices: - chemical - spheroidal - cavitation - isothermal A:
Answer: isothermal

Question: Answer the following question given this paragraph: Soil erosion is a natural occurrence. However, human activities have greatly accelerated soil erosion. In some locations, soil may now be eroding about 10 times faster than its natural rate. Since Europeans settled in the United States, approximately one-third of the topsoil has eroded away. Q: Since europeans settled in the united states, about what percentage of topsoil has eroded away? Choices: - 42 percent - 10 percent - 25 percent - 33 percent A:
Answer:
33 percent