Which statement is true regarding the relationship between air pressure and altitude?

• A. As one moves up in the atmosphere, pressure decreases; as one moves closer to the Earth's surface, pressure increases
• B. As one moves up in the atmosphere, pressure increases; as one moves closer to the Earth's surface, pressure decreases
• C. Pressure remains constant with altitude
• D. Pressure fluctuates randomly with altitude

Answer: (D)

Air pressure comes from the weight of all the air above us. As you rise in the atmosphere, the column of air above you gets smaller, so there are fewer air molecules pressing down. That means the pressure decreases with altitude. It’s not constant, and it isn’t higher up either. Local weather and turbulence can cause small, short‑term fluctuations, but the general pattern is a steady drop in pressure as you go higher. In the standard atmosphere, this drop happens quite noticeably—from about 101 kPa at sea level to much lower values at higher elevations—so pressure falls off with height rather than increasing, staying constant, or changing randomly.