At my house there is never enough work to do after school.
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I remember the first time I saw a lamb born on our farm.
I'm comfortable seeing life and death on the farm.
调节心血管活动的基本中枢位于
A. 脊髓
B. 延髓
C. 脑桥
D. 中脑
E. 小脑
心迷走中枢兴奋时血压下降的主要原因是
A. 静脉回心血量减少
B. 心输出量减少
C. 搏出量减少
D. 外周阻力降低
E. 心肌收缩力减弱
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