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

1. a)c-14 has two more protons

2. d)they have different numbers of protons, neutrons, and valence electrons; they are all gases at room temperature.

3. c) iron and nickel.