Measurements Indicate That a Certain Star Has a Very High

Multiple Choice

Measurements indicate that a certain star has a very high luminosity (100,000 times as bright as the Sun) and yet is relatively cool (3500 K) . How can this be?

A) The star must be quite small.
B) The star must be very large.
C) There must be an error in observation because no star can have these properties.
D) The star must be in the upper part of the main sequence.