每搏输出量和外周阻力不变时，心率降低可引起下列哪一项增加

A．动脉收缩压

B．动脉舒张压

C．动脉平均压

D．动脉脉搏压

E．心搏出量

----It is ______ that self-protection education is required at school.

----I agree. We always have a large course ______ months.

A．certainly; every a few

B．certain; every few

C．sure; every a few

D．surely; every few