The following is a table used for a sporting goods store to track the type of shoes that are available for sale.

$\backslash$table$[[$ShoelD$,$Brand,Type,Price,Color$],[1001,$Nike,Air Max,$$100\mathrm{.}00,$Blue$],[1002,$Reebok,Instant,$$55\mathrm{.}00,$White$],[1003,$Puma,Classic,$$80\mathrm{.}00,$Brown$]]$

Which field is the best choice for the primary key?