${?}_{{?}_{{?}_{?}}{?}_{{?}_{?}}{?}_{{?}_{?}}{?}_{{?}_{?}}{?}_{{?}_{?}}{?}_{{?}_{?}}{?}_{{?}_{?}}\text{A}\text{l}\text{l}\text{i}\text{a}\text{n}\text{c}\text{e}\text{s}\text{a}\text{r}\text{e}\text{c}\text{o}\text{o}\text{p}\text{e}\text{r}\text{a}\text{t}\text{i}\text{v}\text{e}\text{a}\text{g}\text{r}\text{e}\text{e}\text{m}\text{e}\text{n}\text{t}\text{s}\text{b}\text{e}\text{t}\text{w}\text{e}\text{e}\text{n}\text{t}\text{w}\text{o}or\text{m}\text{o}\text{r}\text{e}\text{f}\text{i}\text{r}\text{m}\text{s}\text{f}\text{r}\text{o}\text{m}}$

different national backgrounds.

$a.$

cross$-$border

$b.$

Sector

$c.$

Market

$d.$

Company