With Our Current Techniques, Astronomers Can Typically Only Measure the Minimum

Multiple Choice

With our current techniques, astronomers can typically only measure the minimum mass of a planet orbiting another star. To know the precise mass of the planet, they must also be able to determine

A) the age of the star
B) the angle at which the planet's orbit is tilted relative to us
C) whether the planet has any moons
D) the time the planet takes to make one orbit
E) the language the planet's inhabitants speak, so we can ask them