Which of the following is similar in meaning to ‘flowing’ as used in the passage?

Directions: Read the following passage carefully and select the most suitable option according to the corresponding number in the passage.

All life forms need (1) air and water. They are very important for living things. We can feel air all around us, but we cannot see or hold it. That's becoze (2) air is made up of gases. Gases are stuff (3) like steam, but they are so light that you cannot see or touch them. Some gases mixed in air are very important for life. We also find them in water when air mixes (4) with water. That happens whenever air touches water. Living things get these gases by taking in (5) either air or water. They drive out (6) harmful gases and things from their bodies with the air or water they pass out. The air and water flowing (7) in and out of living things keep the clock of life (8) ticking inside them.