Answer Happy

Determine whether the following subsets of R3 are vector subspaces. A. S={(x,y,z)∈R3∣x=y} B. T={(x,y,z)∈R3∣y=1} C. U={(x,y,z)∈R3∣xyz=0} D. V={(x,y,z)∈R3∣x+y+z=0}