[单项选择]Firewall is a mechanism used by organizations to protect their LANs from the Internet．
A. reliable
B. stable
C. peaceful
D. security

[单项选择]Firewall is a mechanism used by organizations to protect their LANs from the Internet．
A. reliable
B. stable
C. peaceful
D. security

[单项选择]Firewall is a (74) mechanism used by organizations to protect their LANs from the Internet.
A. reliable
B. stable
C. peaceful
D. security

[单项选择]The defense mechanism commonly used by clients who are drug addiction is
A. Denial
B. Projection
C. Displacement
D. Compensation

[单项选择] (15) is a mechanism used for protecting the users outside of network from accessing some non-authorized computer resources.
A. Router
B. Network Card
C. Firewall
D. Protocol

[单项选择]（）is a mechanism used for protecting the users outside of network from accessing some non-authorized computer resources.
A. Network Card
B. protocol
C. Firewall
D. Router

[单项选择]How many media organizations allegedly evaded in taxes according to the probe results
A. 3.
B. 6.
C. 20.
D. 23.

[单项选择]A. He used to live in the country. B. He used to work in the city.
C. He works in the city. D. He lives in the country.

[单项选择]The antigen-antibody immunological reaction used to be regarded as typical of immunological responses. Antibodies are proteins synthesized by specialized cells called plasma cells, which are funned by lymphocytes (cells from the lymph system when an antigen, a substance foreign to the organism’s body, comes in contact with lymphocytes. Two important manifestations of antigen- antibody immunity are lysis, the rapid physical rupture of antigenic cells and the liberation of their contents into the surrounding medium, and phagocytosis, a process in which antigenic particles are engulfed by and very often digested by macrophages and polymorphs. The process of lysis is executed by a complex and unstable blood constituent known as complement, which will not work unless it is activated by a specific antibody; the process of pbagocytosis is greatly facilitated when the particles to be engulfed are coated by a specific antibody directed against them.
The reluctance to abandon this hypothesi
A. proteins existed in specific group types
B. proteins could have been shown to direct the synthesis of other proteins
C. antigens were always destroyed by proteins
D. antibodies were composed only of protein

[单项选择]

We are so used to our life on the surface of the earth that it can be quite an effort for our mind to break free of all the ideas that we take for granted. Because we can feel that things are heavy, we think of "weight" as being a fixed quality in an object, but it is not really fixed at all. If you could take a one-pound packet of butter 4,000 miles out from the earth, it would weigh only a quarter of a pound.
Why would things weigh only a quarter as much as they do at the surface of the earth if we took them 4,000 miles out into space The reason is this: All objects have a natural attraction for all other objects; this is called gravitational attraction. But this power of attraction between two objects gets weaker as they get farther apart. When the butter was at the surface of the earth, it was 4,000 miles from the center. When we took the butter 4,000 miles out, it was 8,000 f
A. it is too small to have a gravitational pull of its own
B. its pull is so small that we tend to ignore it
C. its pull disappears in the presence of the earth’s gravitation
D. it tends to melt and loses its gravitational pull