<p>In believing that firsthand experience would add to the credibility of her biography of Matthew Henson, a discoverer of the North Pole, the author spent a winter north of the Arctic Circle.</p>
<p>A. In believing that
B. Believing that
C. Because believing that
D. She believed that
E. Since having believed that</p>
<p>What's the difference between choice A and B?</p>