Migration, very common among insects and birds, is driven by weather changes. During the cold winter period, food is incredibly inadequate for the animals to carry on, so they make remarkable migrations to find warmer places and to forage. Although most migrating insects only go short distances, particular insects fly very long distances. For example, monarch butterflies spend the summer in Canada and the Northern U.S, and afterward migrate as far south as Mexico for the winter. Many birds migrate in the fall and fly extremely far. For instance, arctic terns nests near the North Pole in the summer. In autumn, they fly south all the way to Antarctica and return to the north each spring.1. What is the main idea of the passage?
a. Insects and birds migrate to keep alive
b. Animal migration can cover long distances
c. Insects and birds migrate in large flocks

2. What is the topic of the passage?
a. Harsh weather
b. Food insuffiency
c. Insects’ and birds’ migration.