Which of these is a subspace of R3\mathbb{R}^3R3?
All (x,y,z)(x, y, z)(x,y,z) such that x+y+z=1x+y+z=1x+y+z=1
All (x,y,z)(x, y, z)(x,y,z) such that x2+y2=0x^2 + y^2 = 0x2+y2=0
All (x,y,z)(x, y, z)(x,y,z) such that xy=0xy=0xy=0
All (x,y,z)(x, y, z)(x,y,z) such that x+y=0x+y=0x+y=0 and z=0z=0z=0