A pendulum energy with each swing.

a.)
gains
b.)
loses

b) loses.

Explanation: As the pendulum swings back and forth, the balance between the two types of energy changes constantly. At some points in its swing, the pendulum has more kinetic energy. At other points, it has more potential energy. No pendulum can swing forever because the system loses energy on account of friction.

Loses i think

Explanation:

its due to the friction of the rope

indicate valleys, hills, steepness and gentleness of slopes.

explanation:

contour lines on a map indicate elevation, or depth. numeric notations on contour lines refer to the level of elevation, or height about sea level.

increased stability in the completion of fluorine's outer shell.