The columns of an invertible n times n matrix form a basis f
     The columns of an invertible n times n matrix form a basis for R^n.  b. The column space of an m times n matrix is a subspace of R^m.  c. The set of all solutions of a system of m homogeneous equations in n unknowns is a subspace of R^n.  d. If B is an echelon form of a matrix A, then the pivot columns of B form a basis for the column space of A.  e. The null space of an m times n matrix is a subspace of R^m. 
  
  Solution
a) True ( The column of an invertible nxn matrix form a basis for Rn)
b) True ( The column space of an mxn matrix is a subspace of Rm)
c) False
d) False. It is the corresponding columns in A
e) True

