Seismologists studying the earthquake that struck northern California in October 1989 are still investigating some of its mysteries：the unexpected power of the seismic waves, the upward thrust that threw one man straight into the air, and the strange electromagnetic signals detected hours before the temblor.

• Athe upward thrust that threw one man straight into the air, and the strange electromagnetic signals detected hours before the temblor  
• Bthe upward thrust that threw one man straight into the air, and strange electromagnetic signals were detected hours before the temblor  
• Cthe upward thrust threw one man straight into the air, and hours before the temblor strange electromagnetic signals were detected  
• Done man was thrown straight into the air by the upward thrust, and hours before the temblor strange electromagnetic signals were detected  
• Eone man who was thrown straight into the air by the upward thrust, and strange electromagnetic signals that were detected hours before the temblor