Passage One
Questions 26 to 28 are based on the passage you have just heard.

A．Scientists have not discovered one single warning sign for all quakes.
B．Scientists have not yet discovered any sign that would tell the size of quakes.
C．Scientists claimed that they had found some methods of predicting earthquakes, but they didn’t work.
D．The methods scientists boasted of 20 years ago of predicting quakes didn’t produce desired results.