X射线机图像中，物体密度越大，（）越大。 A.亮度 B.黑度 C.灰度 D.浓度

图所示，电阻R₁标着“10 Ω l A”，R₂标着“5Ω1.2A”，电流表A₁、A₂量程均为0～3 A，电压表量程0-l5 V，在a、b之间接入电压可调的电源。闭合开关s后，为保证R₁、R₂均不损坏，则允许加的电源电压和通过电流表A₁的电流不得超过

A．16 V 1 A

B．10 V 2.2 A

C．6 V 2.2 A

D．6 V 1.8 A

IPv6 is short for "Internet Protocol Version 6". IPv6 is the "next generation" protocol designed by the IETF to (71) the current version Internet Protocol, IP version 4("IPv4").
Most of today’s internet uses IPv4, which is now more than twenty years old. IPv4 has been (72) resilient in spite of its age, but it is beginning to have problems. Most importantly, there is a growing (73) of IPv4 addresses, which are needed by all new machines added to the Internet. IPv6 fixes a number of problems in IPv4, such as the (74) number of available IPv4 addresses. It also adds many improvements to IPv4 in areas such as routing and network autoconfiguration. IPv6 is expected to gradually replace IPv4, with the two coexisting for a number of years during a transition (75) .

A．restrict

B．confine

C．limited

D．imprison

—Did you have a talk with Tom?

—No.I was trying to _________ a chance to do so,but I failed.

A．seize

B．grasp

C．form

D．catch

小型消毒如游泳池水消毒等，多采用（）发生器。

A、氯胺

B、漂白粉

C、液氯

D、次氯酸钠

正常人尿中偶可见到

A．白细胞管型
B．红细胞管型
C．透明管型
D．蜡样管型
E．上皮细胞管型