Why is the statement in (a) true? A. The columns of a matrix A are linearly independent if and only if the equation Axequals=0 has more unknowns than equations so there must be free variables. This happens if and only if there are m pivot columns. B. The columns of a matrix A are linearly independent if and only if the equation Axequals=0 has only the trivial solution. This happens if and only if Axequals=0 has no free variables, meaning every variable is a basic variable, that is, if and only if there are 0 pivot columns. C. The columns of a matrix A are linearly independent if and only if Axequals=0 has no free variables, meaning every variable is a basic variable, that is, if and only if every column of A is a pivot colunm.