填句补文
Every year, millions of birds fly long distances from one place to another. __26__ this is called migration(迁徙). Birds migrate to find better living conditions, especially food and a suitable place to breed. Migration is a difficult journey, but it is necessary for the survival of many bird species. __27__ Most birds migrate in autumn and spring. In autumn, as the weather gets colder, food becomes scarce in the north. So birds fly to warmer southern areas where there is plenty of food. In spring, the weather gets warmer in the north, and food becomes abundant again.
Birds fly back to the north to breed, because the northern areas have more space and fewer enemies for their young. __28__
Birds have amazing abilities to find their way during migration. Some birds use the sun and the moon to navigate. They can tell direction by the position of the sun during the day and the moon at night. __29__ Other birds use the Earth’s magnetic field to find their way, they have a special sense that allows them to feel the magnetic field, like a built in compass. __30__
Migration is a dangerous journey. Birds face many challenges, such as bad weather, lack of food and water, and enemies. Some birds fly for days or even weeks without stopping. To prepare for migration, birds eat a lot of food to build up fat reserves, which provide them with energy during the long flight.

选项：
A.The bands contained a name and address
B.Birds use the earth's magnetic field to navigate a map
C.Long-distance travel requires a compass to navigate a map
D.They learn the routes of miles from one home to another
E.They fly thousands of miles from the geese have traveled before
F.They have answered many questions about how birds navigate