To solve this question, we need to understand the effect of gravitational force on weight, which is a product of mass and gravitational acceleration. The formula for weight (\(W\)) is:

\(W = mg\)

where:

• \(m\) is the mass of the object (in kilograms).
• \(g\) is the acceleration due to gravity (in meters per second squared).

On Earth, the gravitational acceleration is approximately \(9.8 \, m/s^2\). On the Moon, however, it is about one-sixth of Earth's gravity, which is approximately \(1.63 \, m/s^2\).

Given that the astronaut weighs 600 N on Earth, we can find her weight on the Moon using the ratio of the gravitational forces. Since the Moon's gravity is about one-sixth of Earth's:

\(\text{Weight on the Moon} = \frac{1}{6} \times \text{Weight on Earth}\)

Substituting the given weight on Earth:

\(\text{Weight on the Moon} = \frac{1}{6} \times 600 \, \text{N} = 100 \, \text{N}\)

Therefore, the closest value to her expected weight on the Moon is 100 N. The option "100 N, because the Moon's gravity is about one-sixth of Earth's" is correct.

Let's analyze the other options to understand why they are incorrect:

• 200 N, because the Moon's gravity is about one-third of Earth's: Incorrect, as the Moon's gravity is approximately one-sixth, not one-third, of Earth's gravity.
• 600 N, because a person's weight remains unchanged on the Moon: Incorrect, because weight depends on local gravitational force, which is different on the Moon.
• 300 N, because the Moon's gravity is about one-half of Earth's: Incorrect, as the Moon's gravity is about one-sixth of Earth's.