1 . I didn’t see Peter enroute (在途中) but reunited back ________ we started, both of us sheepish but pleased. （用适当的词填空）

2 . Natural bird habitats are most commonly found ________ there is an ample supply of water for drinking, swimming, and bathing. （用适当的词填空）

3 . Like any natural force, gravity pull can work with us or not. The gravity pull of our habits may currently be keeping us from going ________ we want to go. （用适当的词填空）

4 . I wish my house would be built______we can enjoy beautiful scenery with mountains and rivers. (用适当的词填空)

5 . To take back our beautiful countryside and cities, we need to do more than simply not leaving rubbish ________it ought not to be. We need to truly care more about the world around us. (用适当的词填空)

6 . After six-and-a-half years and over 32, 000 kilometers, Maxwell’s walk ended __________it began. (用适当的词填空)