There are ______ Russian（s) and ______ American（s) on board.A．one, oneB．one, twoC．two, two

There are ______ Russian(s) and ______ American(s) on board.

A．one, one

B．one, two

C．two, two

D．two, one

请帮忙给出正确答案和分析，谢谢！