Which matrix is not invertible?

Question

1) 2 0 -1

3 1 0

3 3 3

2) 0 3 0

3 0 3

3 0 2

3) 1 0 0

0 1 0

0 0 1

4) 1 1 1

0 1 1

0 0 1

Answer 1

Which one has columns (or rows) that are not independent is another way of asking this question. By "independent" we mean which matrix has columns (or rows) such that you can't scale and sum any two to equal the third? (3) is definitely out. The three columns denote the x, y and z coordinate directions and there's no way you can add, say, y and z coordinates together to change x.