# Dimensionless quantity

$(a)\;may \;have\;a\;unit\quad (b)\;never\;have\;a\;unit\quad (c)\;always\;have\;a\;unit \quad (d)\;does\;not\;exist$

Some dimensionless quantities have units , for example Angle- unit Radians and Solid angles - unit Steradian
answer- may have units
Hence a is the correct answer.
answered Jun 17, 2013 by
edited Jan 9, 2014 by meena.p