国家实行无偿献血制度。国家提倡十八周岁以上的健康公民自愿献血。（）
参考答案：错
He had a lot of friends, only a few of _________ invited to his wedding.
A．whom
B．them
C．which
D．who
铁水处理设备包括（）和（）两种。
