What queuing system is most common at banks when waiting for a$$ teller?

Part $2$

A$.$

$$Finite$-$population model

B$.$

$$Single$-$service system$($M$/$M$/1)$

C$.$

Constant service$($M$/$D$/1)$

D$.$

$$Multiple$-$server $($M$/$M$/$S$)$