1．(2018·全国卷Ⅰ)Join a ________(guide) bike tour and view some of the most popular monuments in Washington, D．C.
[答案] guided
2．(2018·全国卷Ⅰ)Making lovely objects using ________ (recycle) and made materials.
[答案] recycled
3．(2018·北京卷)But compared with ________(previously) studies, she finds the speed of breaking down in this one exciting.
[答案] previous
4．Though ________(lack) natural resources，the area is well developed.
[答案] lacking
