管内导线包括绝缘层在内的总截面积不应大于管子内面积的（）。 A.60％ B.50％

相内含的两圆的圆心距为2cm，可作两圆半径的是（　　）

A．4cm和1cm

B．5cm和3cm

C．6cm和5cm

D．4cm和2cm

一条河宽100米，船在静水中的速度为4m/s，水流速度是5m/s，则（   ）

A．该船可能垂直河岸横渡到对岸

B．当船头垂直河岸横渡时，渡河所用的时间最短

C．当船横渡时与岸的夹角可能为60°

D．当船横渡到对岸时，船对岸的最小位移是125米

外界物体反射来的光线，由瞳孔进入眼球内部，再经过一系列折射后，物像形成于 [ ]

A．角膜

B．视网膜

C．晶状体

D．视觉中枢

周围血反应骨髓幼红细胞增生程度准确的指标是（）

A.网织红细胞百分数

B.血红蛋白和红细胞数

C.网织红细胞绝对数

D.出现有核红细胞

E.出现染色质小体

In the following essay, each blank has four choices. Choose the most suitable one from the four choices and write down in the answer sheet.

The key to SNMP (76) is its simplicity. It has a small command set that does a good job of collecting information from (77) any network device. In a SNMP environment, (78) of the work is handled by the network management system. Devices that are being managed are not (79) with processing (80) that might affect their performance.

（76）是（）

A. many

B. almost

C. a lot of

D. nearly