Response: Options a, b, c, d is all correct. All of these can be used to remove the legend. We use legendTest + guides(fill=FALSE) to remove legend for a particular aesthetic. This can also be possible in option b which is using the scale_fill_discrete() function when specifying the scale. The third option in option c which is legendTest + theme(legend.position="none") will remove all legends in the plot. Option d also has similar syntax format as in option a which will enable to remove the legend.