Lily was talking to our teacher about examination, when suddenly Tom _______.

A．cut off

B．cut out

C．cut up

D．cut in

有关脊麻时低血压的原因，哪项正确（）

A.阻滞交感神经节前纤维

B.阻滞支配肾上腺髓质的神经

C.阻滞副交感神经纤维

D.肌肉松弛

E.术前脱水