\text{adddef=No. <i>F</i> is not stable under addition}
\text{muldef=No. <i>F</i> is not stable under multiplication by scalar}
\text{empty=No. <i>F</i> is empty}
\text{yes=Yes. <i>F</i> is effectively a vector subspace}
\text{choices=\adddef,\muldef,\empty,\yes}
