Please help with the following?

"In this question we will prove that certain sets are not subspaces by finding an example which demonstrates that they are not closed under vector addition. For each set W, give two vectors u∈Wand v∈Wfor which u+v∉W. Enter a list of vectors in the format [1,2,3],[3,4,5] for example.

(a) W1 = {(x,y)∈ℝ^2:xy≥0}
(b) W2 = {(x,y,z)∈ℝ^3:x+2+3z=1}
(c) W3 = {(1,2,0)+s(1,1,1):s∈ℝ}
(d) W4 = {s(1,2,2):s∈ℝ}∪{t(2,3,3):t∈ℝ}"