[单项选择]Nowadays, skilled workers such as carpenters, electricians and TV repairmen often have higher income than college graduates. The old distinction that white-collar workers make a better living than blue-collar workers no longer______ true.


A. hold
B. stay
C. come
D. become

[单项选择]Nowadays groups of scientific workers, often supposed by their governments, spend their time studying the occurrence of earthquakes. It is very likely that they will be able to (47) earthquakes or influence the direction of their movements, which are determined by events far below the surface of the earth. But the facts they report and the theories suggested by those facts may enable scientists to (48) the centers of future earthquakes and even predict the time of their occurrence. It is only when the (49) of events that we call an earthquake can be seen as a pattern that predictions can be made. Part of its pattern is external and visible, or capable of being recorded by sensitive instruments above the earth’’s surface. Scientists and engineers studied the shock waves of the San Francisco earthquake. Tile city was rebuilt and new features were (50) to strengthen buildings and (51) a constant water supply in the event of another earthquake. Large underground tanks w