题目内容：
The root systems of certain plant families, such as that of tulips and crabgrass, __________ underground, so that nutrients may be shared along __________ network.
参考答案：
答案解析：
单选题：The root systems of certain plant families, such as that of
- 题目分类：GRE
- 题目类型：单选题
- 查看权限：VIP