1. Files and rats are household _________.

　　　 A. pets　　　　　 B. pests　　　　 C. friends　　　 D. insects

62. They eat constantly to build up a reserve of fat.

61. Most penguins can go without eating for weeks during breeding periods.

60. They use their webbed feet as rudders to change direction and as brakes.

59. They slide on their bellies to move faster when they go downhill.

58. They walk with a clumsy waddle or a hop.

57. They are graceful and fast.

56. No, they are not able to do so.

55. Emperor and Adelie are two species of penguins.

39. He walked up the stage to receive his prize.