For which of the following compounds is it possible to make
a $1.0 M$ solution at $20^{\circ} \mathrm{C} ?$
a. $\mathrm{CuSO}_{4},$ solubility $=32.0 \mathrm{g} / 100 \mathrm{mL}$
b. $\mathrm{Ba}(\mathrm{OH})_{2},$ solubility $=3.9 \mathrm{g} / 100 \mathrm{mL}$
c. $\mathrm{FeCl}_{2}$, solubility $=68.5 \mathrm{g} / 100 \mathrm{mL}$
d. $\mathrm{Ca}(\mathrm{OH})_{2},$ solubility $=0.173 \mathrm{g} / 100 \mathrm{mL}$