# Boolean Algebra – 4

4. The Boolean expression for the sub-class(R) of all digital electronics instruments which are not measuring instruments and have no battery supply is :

(a)  $\dpi{80} R+X+YZ$
(b)  $\dpi{80} R=XY+Z$
(c)  $\dpi{80} R=\bar{X}\bar{Y}\bar{Z}$
(d)  $\dpi{80} R=XYZ$