The correct answer is option 3: Only the oscillation method.

In a space-station orbiting Earth, there is no gravity acting on objects in the same way as on Earth`s surface. Option 1, which is both methods, cannot be used because measuring the extension in the spring due to the object relies on the force of gravity. Without gravity, there will be no extension in the spring, making this method invalid.

Option 2, which is only the extension method, also cannot be used because it relies on the force of gravity. Similar to option 1, without gravity, there will be no extension in the spring.

Option 3, the oscillation method, is the correct answer. This method measures the oscillation period of an object attached to a spring. The period depends on the mass of the object and the stiffness of the spring. In a space-station orbiting Earth, the oscillation method can still be used because it relies on the mass of the object and the properties of the spring, independent of gravity.

Option 4, neither method, is not correct as the oscillation method can still be used in a space-station orbiting Earth.