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

A．The surface of the ocean is expanding.
B．The surface of earth contains tons of cosmic dust.
C．Volcanic activity is increasing.
D．Thousands of comets are colliding with earth’s atmosphere.

A．From the western United States.
B．From only the east coast of the American Continent.
C．From all parts of the country.
D．From San Francisco Bay.