"This is one of the unsolved mysteries of long-distance flights," Klaassen said.
“这是长距离飞行的不解之谜之一，”克拉森说。
2
By Martine Klaassen Armed with two over-packed suitcases, we arrived at the airport just in time for my flight.
日记 我们提着满满的两个行李箱，及时到达机场赶上了我的航机。
3
But it's these ample fat reserves that allow the birds to fly such long distances without stopping, said study leader Raymond Klaassen, a biologist at Sweden's Lund University.