Which of the following are legal Python variable names?

$($a$)$ var$2$

$($b$)\_$var$2$

$($c$)-$var$2$

$($d$)+$var

$($e$)$ var $2$

$($f$)$ var$\_2$

$($g$)$ var$-2$

$($h$)$ var$2\_\_\_\_$

$($i$)2$var

$($j$)$ var@