休克治疗时应用血管活性药物的目的是

A．升高血压

B．提高组织器官的血液灌流

C．提高心脏前负荷

D．提高心脏后负荷

E．增加心肌收缩力

IP multicasting is a set of technologies that enable efficient delivery of data to manylocations on a network．Rather than making multiple copies of a message intended to bedistributed to multiple recipients at the (71) of origin of a message，multicasting initiallysends just one (72) and does not copy it to the individual recipients until it reaches theclosest common point on the network，thereby (73) the bandwidth consumed．Networkperformance is significantly (74) because it isn’t bogged down with the processing andtransmission of several large data files；each receiving computer doesn’t have to (75) thetransmitting server for the file．

A．extending
B．minimizing
C．demolishing
D．reducing