—How many times have you been to China?

—In fact, it is the first time I __________ here.

A．was

B．am

C．had been

D．have been

尿毒症酸中毒纠正后，患者发生抽搐，此时最迅速有效的治疗措施是（）

A.口服碳酸钙片

B.肌注安定

C.口服氢氧化铝凝胶

D.肌注VitD₃

E.静注葡萄糖酸钙