What does it mean to span in R2? I have this question:

Which of the following sets if vectors span R2?
a) {(1,1),(-2,-2)}
b) {(1,1),(1,2)}
c) {(1,2),(1/2,2)}
d) {(-1,1),(1,-1)}

They span R2 if they are independent. That is, the 2nd is not a multiple of the 1st.

So, what do you think?