Oxygen is the primary chemical in the decomposition of organic organisms
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
D- The digestive system breaks down your food and your circulatory system takes it throughout your body
The correct answer is letter "B. Conical shape ." The characteristic of a pine tree is an adaptation to the climate of the northwestern coniferous forests is that it is in conical shape. If C were needle like leaves that would be the best answer.
