"Are you sure it is alive (活着)?"asked Jack. "I don't see it 1 . "He was looking at a sloth (树懒). I moves so slowly that people can not find it and it always looks asleep. "
It is the slowest-moving mammal (哺乳动物)in the world" the 2, Alex who has looked after the sloth for six years in the zoo told Jack. "It can't walk. On the 3, they move hand over hand slowly. This makes them easy to catch. They stay in the trees to 4 themselves from bigger animals. "
"So how slow is it?" Jack asked. Alex told Jack to 5 where the sloth was. And then Jack saw that it was 6 a branch (树枝).
Then Jack went to lunch. He ran quickly and couldn't wait to see the sloth after lunch and expected to see the 7. It only moved past the branch! Jack was 8.
"See, said Alex. "We can 9 how fast it moves. A sloth on the ground can only move 6—8 feet per minute. In a tree, a sloth can move 10 . It can move 15 feet. "
