All vectors and subspaces are in ${\mathbb R}^n$.

Check the true statements below:

A. If $x$ is not in a subspace $W$, then $x-{\rm proj}_W(x)$ is not zero.
B. If $W=Span \{x_{1},x_{2},x_{3} \}$ with $\{x_{1},x_{2},x_{3} \}$ linearly independent, and if $\{v_{1},v_{2},v_{3} \}$ is an orthogonal set in $W$, then $\{v_{1},v_{2},v_{3} \}$ is an orthogonal basis for $W$.
C. In a $QR$ factorization, say $A=QR$ (when $A$ has linearly independent columns), the columns of $Q$ form an orthonormal basis for the column space of $A$.