In Recent Decades, Astronomers Discovered Stars Even Cooler Than the Traditional

Multiple Choice

In recent decades, astronomers discovered stars even cooler than the traditional spectral type M stars recently. Astronomers gave these cool stars a new spectral type, L. If you wanted to go out and find more such type L stars, what kind of instrument would it be smart to use?

A) an x-ray telescope, in orbit above the Earth's atmosphere
B) a sensitive infra-red telescope
C) a small visible-light telescope (something even an amateur astronomer or small college might have)
D) a CCD attached to an ultra-violet telescope
E) a swimming-pool size vat of commercial cleaning fluid, deep in an abandoned mine