TOEFL Reading: ETS-TOEFL阅读机经 - CA3OY0CCH3834GHEL$

According to the theory discussed in paragraph 3, a weakening of Earth's magnetosphere may have A. caused a supernova to explode near our solar system B. allowed gene-altering particles to reach Earth's surface C. forced Earth's magnetic field to change direction D. allowed clouds of protective particles to escape from Earth's upper atmosphere