Some Exoplanets Appear to Have Very Surprising Characteristics, Namely Jupiter-Like

Multiple Choice

Some exoplanets appear to have very surprising characteristics, namely Jupiter-like masses but very small orbital radii. However, an uncertainty in observational precision may render this observation meaningless. What uncertainty is this?

A) The radial velocity method can only give a lower limit for a planet's mass, so exoplanets could be massive brown dwarf or low-mass stars.
B) The astrometric method can only give an upper limit for a planet's mass, so exoplanets could be terrestrial planets.
C) The astrometric method can only give a lower limit to the orbital radius, so exoplanets could be orbiting at the proper distance expected for a jovian planet.
D) The radial velocity method cannot distinguish between orbital variations due to a planet and stellar pulsations where the radial velocity variations are caused by the motion of the star's surface. Thus, there may be no planets at all.