填空题

Directions: This section is to test your ability to comprehend short passages. You will hear a recorded passage. After that you will hear five questions. Both the passage and the questions will be read two times. When you hear a question, you should complete the answer to it with a word or a short phrase ( in no more than 3 words) . The questions and incomplete answers are printed in your test paper. You should write your answers on the Answer Sheet correspondingly. Now the passage will begin.
How many earthquakes happen every year __________.