Which of the following molecules are NOT covalently attached to proteins as post-translational modifications?

W) Ubiquitins

X) Phosphates

Y) Ions such as Ca\({}^{+2}\) and Mg\({}^{+2}\)

Z) Carbohydrate groups
Y) IONS SUCH AS Ca\({}^{+2}\) AND Mg\({}^{+2}\)