—How long have they _____?  

—They _____ more than twenty years ago. [ ]

A. been married; got married          

B. married; married

C. got married; were married          

D. got married; got married

镁的主要生理功能为

A．镁与钙在体内具有协同作用

B．对神经、肌肉的兴奋性有镇静作用

C．构成核苷酸类辅酶

D．调节渗透压

E．维持酸碱平衡