Answer the following question given this paragraph: So how is the blood kept from flowing back on itself? Valves ( Figure below ) in the heart keep the blood flowing in one direction. The valves do this by opening and closing in one direction only. Blood only moves forward through the heart. The valves stop the blood from flowing backward. There are four valves of the heart. Q: How many valves are in the heart? Choices: - one - six - two - four A:
four

Answer the following question given this paragraph: Static electricity is a buildup of electric charges on objects. Charges build up when negative electrons are transferred from one object to another. The object that gives up electrons becomes positively charged, and the object that accepts the electrons becomes negatively charged. This can happen in several ways. Q: What type of electricity is formed when a negative charge builds up and are transferred? Choices: - neutron energy - alternating current - direct current - static electricity A:
static electricity

Answer the following question given this paragraph: A food chain represents a single pathway by which energy and matter flow through an ecosystem. An example is shown in Figure below . Food chains are generally simpler than what really happens in nature. Most organisms consumeand are consumed bymore than one species. Q: A single, often oversimplified, path through which energy and matter flow through an ecosystem is also known as what? Choices: - the chain - fuel chain - life cycle - food chain A:
food chain

Answer the following question given this paragraph: The core is the Sun's innermost layer. The core is plasma. It has a temperature of around 15 million degrees Celsius (C). Nuclear fusion reactions create the immense temperature. In these reactions, hydrogen atoms fuse to form helium. This releases vast amounts of energy. The energy moves towards the outer layers of the Sun. Energy from the Sun's core powers most of the solar system. Q: What is the suns innermost layer called? Choices: - surface - solar - flare - core A:
core