肾缺血或中毒时,引起系膜细胞收缩的内源性因子是()
A.腺苷
B.硝酸甘油
C.前列腺素E2(PGE2)
D.前列腺素A2(PGA2)
E.抗利尿激素(ADH)
参考答案:E
By the time I got to the airport, the plane . [ ]
A. took off
B. has taken off
C. had taken off
GPS卫星同步时钟在电力系统自动化领域有何用途?