typical explore urban research extreme mobile 4. If you are , you can move or travel easily from place to place. 5. A computer user spends 6 hours on social networking sites. 6. What sports do you like most? I love scuba diving. 7. If you do , you study something to learn about . 8. means being part of a city or town.

unicellular organisms, like bacteria, are able to perform all life functions within one single cell. multicellular organisms need many different types of cells to carry out the same life processes. each of these special types of cells has a different structure that it perform a specific function.

blood enters the heart through two large veins, the inferior and superior vena cava, emptying oxygen-poor blood from the body into the right atrium of the heart. as the ventricle contracts, blood leaves the heart through the pulmonic valve, into the pulmonary artery and to the lungs where it is oxygenated.