Which is not a valid rule for specifying background image positioning?

All of the above are valid style rules for specifying background image position.

$[$background$-$position: $100$px $100$px; $\}$

$($background$-$position: $50\%50\%$;

$\{$background$-$position: center bottom; $\}$

$\{$ background$-$position: left top; $\}$