读图按要求完成下列各题。 （1）图中字母表示的地理事物为： A________

IP multicasting is a set of technologies that enable efficient delivery of data to many locations on a network. Rather than making multiple copies of a message intended to be distributed to multiple recipients at the (71) of origin of a message, multicasting initially sends just one (72) and does not copy it to the individual recipients until it reaches the closest common point on the network, thereby (73) the bandwidth consumed. Network performance is significantly (74) because it isn’t bogged down with the processing and transmission of several large data fries; each receiving computer doesn’t have to (75) the transmitting server for the file.

A．point

B．bottom

C．head

D．sight

选择性动脉栓塞术主要不适反应不包括（）

A.头痛

B.发热

C.恶心呕吐

D.全身瘙痒

E.腹部内脏血管栓塞区疼痛

下列气体中，不能作喷泉实验的是(括号内为溶剂)    (  )

A．CO₂(NaOH)

B．SO₂(NaOH)

C．NH₃(H₂O)

D．NO(NaOH)

断续周期工作制的工作周期一般为（）。

A.≤10min

B.≤20min

C.≤35min

D.≤30min

（）不属于邀请招标的范围。

A、技术要求较高、专业性较强的招标项目

B、合同金额较小、工期要求较为紧迫的招标项目

C、有特殊要求或保密的工程

D、建设资金50万以上的工程