Explanation:

- A second's pendulum has a time period of 2 seconds (one-second swing each way).

- The standard length for a second's pendulum on Earth at sea level is about 1 meter.

- Here, the given length is 10 cm, much shorter than 1 meter.

- This short length can only be a second's pendulum if the acceleration due to gravity (g) is much lower than Earth's surface value.

- Let's look at each option:

- Option 1: At the top of Everest

- Gravity is slightly less than sea level.

- Not enough decrease to make 10 cm a second's pendulum.

- Option 2: Inside a deep mine

- Gravity decreases slightly as you go underground.

- Still, not nearly enough for 10 cm to qualify.

- Option 3: Mars

- Gravity on Mars is about 1/3 of Earth.

- The required pendulum length for a 2s period is still longer than 10 cm.

- Option 4: Moon

- Gravity on the Moon is 1/6 of Earth's.

- This low gravity would require a much shorter pendulum for the same period—10 cm fits closely.

- So, a 10 cm pendulum can behave as a second's pendulum only on the Moon.