The valves are responsible for preventing blood from flowing in the wrong direction, they are present in the veins, and the arteries don't need them because the aorta (biggest artery) pumps or in other words pushes it with such a force that no other force can change its direction, in the veins there is no structure present for pumping them as a result we have got valves so that they go in one direction...... the meaning of the word valve is to allow in one direction
Answer:
Sandstone
Sandstone contains fossils of creatures such as trilobites, brachiopods, crustaceans, bryozoans and plants. Remains of land animals like mastodons and dinosaurs are much more likely to be found in sandstone.
Explanation:
thank me later
Answer:
water and land
Explanation:
I assume this is an open-ended question, so you could make an argument for lots of things, but these are the two most important ones in my opinion. The amount of freshwater on Earth is pretty small, only about 2.5%, and most of that is locked in ice. As the demand for food grows, the demand for water for crops and livestock also grows. This is in addition to the increase in water that is needed for a growing population. Climate change increases this problem because of drought. The second most important resource that will be affected is land. If we need more food, we also need space to grow crops and raise livestock. The available space is also reduced because people need places to live and we need to be able to grow trees for wood to build houses and other buildings. I argue that land and water will be the most in-demand commodities as the population continues to increase.
It contains 4 key elements carbon, hydrogen, oxygen and Nitrogen. so your answer is nitrogen
