Because of ______ high demand for Type AB blood, ______ supplies of it are usually limited.

A．the; the

B．不填; 不填

C．不填; the

D．a; the

正常血压病人血压较麻醉前升高多少，即应视为高血压（）

A.10mmHg

B.20mmHg

C.30mmHg

D.40mmHg

E.50mmHg