百草枯中毒患者考虑吸氧的氧分压浓度需低于()
A.20mmHg
B.30mmHg
C.40mmHg
D.50mmHg
E.60mmHg
参考答案:C
It seems that we ( ) the April shipment.
A. catch B. can catch C. will catch D. have catch
已知x=1是一元二次方程x2-mx+n=0的一个根,则m2-2mn+n2的值为______.