单选题：Solar Storm　　 At the end of October 2003, a sudden solar sto

Solar Storm
　　 At the end of October 2003, a sudden solar storm hit the earth. A solar storm refers to the large amounts of charged particles released into space_________ (51) the solar energy increases. The release of the energy_________ (52) place along with the activity of the sunspots with a cycle of 11 years. This time, the_________ (53) of the storm exceeded expectations.
　　 This_________ (54) of intense solar storm was caused by the eruption of a solar flare (闪光) and the ejection (喷发)of the solar corona (日冠) on October 28, 2003. Large amounts of charged particles moved 150,000,000 kilometers through space toward the_________ (55) in 19 hours. They could affect aircraft roaming (漫游)in space.
The high-energy particles will_________ (56) some of the parts of an aircraft. They may also cause it to fail. High-energy particles can threaten the safety of an aircraft at a high orbit. If an aircraft orbits at a lower orbit, it is_________ (57) because it is under the protection of the earth's magnetic field.
　　 A solar storm not only affects aircraft but also is a_________ (58) to the environment and humans. The aerosphere and magnetic field of the earth can_________ (59) humans from ultraviolet radiation and X-rays. While most of the X-rays are absorbed after they enter the aerosphere (大气层), still a few can_________ (60) the ground.
　　 The geomagnetic storm caused by this round of solar storm reaches its highest level on the two_________ (61) of the earth, which affects electricity supply of North America.Overexposure to_________ (62) threatens the health of passengers on planes flying over the PolarRegions. If we fly in the sky during such a solar storm, it_________ (63)we receive ten times the X-ray radiation. It's really damaging.
　　 Scientists say a solar eruption is like the sun sneezing, which will make the earth_________ (64)a cold.Though this natural force is irresistible, scientists can still_________ (65)its movement accur'ately by monitoring. Facing successive solar storms,humans can't drop their guard. A．since
B．when
C．until
D．though