One astronomer has observed an apparent lengthening of the electromagnetic waves given off by a star. Which of these conclusions is correct about the star? Its parallax is increasing. It is moving towards Earth. Its wavelength is decreasing. It is moving away from Earth.

I think the correct answer from the choices listed above is the last option. The conclusion about the star would be that it is moving away from Earth. L engthening of the waves means that wavelength getting larger this occurs when a body giving off light is moving away. Hope this answers the question.