（接上题）Easy implementation and O(lgn) complexity 需要易于实现，而且各接口的分摊复杂度为O(lgn) A: AVL trees AVL树 B: Splay trees 伸展树 C: B-trees B-树 D: Red-black trees E: kd-trres kd-树

People who love trees may （）. A: never cause trees injury B: damage trees on purpose C: do harm to trees without knowing it D: not be aware of which trees are healthy

People who love trees may ______. A: never cause trees injury B: damage trees on purple C: do some harm to trees without knowing it D: not be aware of which trees are healthy

______ is fun and a great way ______ greenhouse gases. A: Plant trees, reduce B: Planting trees, to reduce C: To plant trees, reduce D: Planting trees, to reducing

The purpose of the passage is to tell ______. A: that people should protect trees B: that people should plant more trees C: what trees can be used for D: what kinds of trees look beautiful

Maple trees are thought to be fall color trees or foliage trees.

In order to protect trees, we should not cut down trees for __________________ chopsticks. A: once B: throwaway

The essential difference between trees and grass is that trees are taller than grass.

There are many___ on the mountain. A: apple tree B: apples trees C: apples tree D: apple trees

Trees _ their leaves .