Passage Two Questions 29 to 31 are based on the passage you have just heard.

A．Hardly ever looked into the causes of tragedies.
B．Imposed safety rules as soon as accidents took place.
C．Seldom introduced safety laws before disasters occurred.
D．Paid much attention to the results of scientific discoveries.

A．They are useful and practical.
B．They are of great importance.
C．They are imaginative and personal.
D．They are fashioned and quick to arrive.