Which of the following affects an aircraft's center of gravity?

The positioning of cargo and passengers directly affects an aircraft's center of gravity because the center of gravity is the point where the weight of the aircraft is balanced. When cargo and passengers are loaded onto the aircraft, their placement alters where the total weight is concentrated. For instance, moving cargo toward the front or rear of the aircraft will shift the center of gravity forward or backward, respectively.

In emphasizing the importance of maintaining an appropriate center of gravity, pilots must consider weight distribution to ensure stability and control throughout the flight. An imbalanced aircraft can lead to poor handling characteristics, increased drag, and even loss of control.

Other factors mentioned, such as the airplane's exterior design, color, and type of fuel used, do not influence the center of gravity directly. The design may affect performance but does not change where the weight is balanced in flight, while color is purely aesthetic and has no impact on the aircraft's physical properties or weight distribution. Similarly, while the type of fuel can affect the total weight of the aircraft, it does not impact the positioning of that weight within the aircraft's structure or the balance of that weight.