5.Suppose Define How many of S1,S2,S3,S4,S5 are subspaces of R3? (A) 1 (B) 2 (C) 3 (E) 5 (D) 4

4. (5%) Let A be an m by n matrix. Which statement is TRUE? (A) The null space of A is a subspace of the column space of AT (B) The dimension of the null space of A plus the dimension of the row space of A is (C) The null space of AT equals column space of A (D) The column space of A is orthogonal to the row space of AT (E) The direct sum of the row space of A and the null space of AT is Rm