Do you know that some have come to our school for a visit

Do you know that some have come to our school for a visit
Do you know that some_____have come to our school for a visit today?
Yes,I saw they were_____in the canteen for lunch.
A.Germans;seated B.German;sat C.Germany;seats D.Germen;sitting
我知道前面一个是用Germans 但后面那个用什么