This german-coined term refers to workers who work in a foreign country, as long as there's work available, but who would eventually return to their respective homelands.

a. resident alien
b. guest worker
c. immigrant
d. temporary worker

Option a resident alien

resident it means coming from other place, not permanent, stranger or a foreigner

classification:
1)legal alien -tourists, legal permanent workers, student-visa, and guest workers
2)nonresident alien-tourist,on business,entertainers,sports people,under medical treatment
3)resident alien-temporary resident
4)enemy alien-national enemy
5)illegal alien- unlawfully authorized, overstayed and cross along the border line 

Amath expression is a collection of one or more terms, which are separated by the signs ( + , - , x , / ).example :   8+b8+b  or  a−3a−3in algebra, an equation is a mathematical statement with two expressions where, each expression is separated by an equal (=) sign. variables can be present on both the sides of the equality (=) sign and we use letters to denote such variables.example 1:   x=4+2x=4+2  , [here, we can observe that the variable is present only on one side of the equation].example 2:   2x+3=x+42x+3=x+4  , [here, we can observe that the variables are present on both side of the equation].