设等差数列{an}的公差d≠0,a1=4d,若ak是a1与a2k的等比中项,则K的值为( ).
3
It is required that each of the students chosen _____ good preparations ahead of time.
A.has to make
B.will make
C.should make
D.must make
心肺复苏的有效指征( )。
A.颈、股动脉可触及搏动
B.散大的瞳孔缩小
C.自主呼吸恢复
D.自行排大小便
E.上肢收缩压在8kPa(60mmHg)以上