Which type of binary can have their sizes measured directly by photometry?

A.Virtual
B.Visual
C.Eclipsing
D.Spectroscopic
E.Astrometric

e. i think

its definatly d

I think Eclipsing binaries. Please see:

http://en.wikipedia.org/wiki/Astrometric_binary

The correct answer is C. Eclipsing binaries. Photometry is a method of measuring the brightness or intensity of an object. In the case of eclipsing binaries, the brightness of the system changes as one star passes in front of the other, causing periodic dips in the total brightness. By analyzing the light curves from these eclipses, astronomers can directly measure the sizes of the stars in the binary system.