If an Astronomer Wants to Find and Identify as Many

If an astronomer wants to find and identify as many stars as possible in a star cluster that has recently formed near the surface of a giant molecular cloud (such as the Trapezium cluster in the Orion Nebula) , what instrument would be best for her to use?

A) an infra-red telescope (and camera)
B) an x-ray telescope
C) a very good camera attached to a large reflector telescope on the ground
D) an ultraviolet spectrograph attached to the Hubble Space Telescope
E) the instruments that were part of the Compton Gamma Ray Observatory