任何一颗二叉树的叶子结点在先序、中序、后序遍历序列中的相对次序（ ）。
A. 肯定不会发生改变
B. 肯定发生改变
C. 不能确定
D. 有时发生变化
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Read Text A, Unit 8, then finish the following exercises.Who is a noted disbeliever in climate change?
A. Boris Johnson.
B. Emmanuel Macron.
C. Jair Bolsonaro
Donald Trump.
Which country decided to dispatch armed forces to fight the fires?
A. Brazil.
Britain.
C. French.
D. England.
which of the follow statement is NOT true according to Brazilian President Jair Bolsonaro?
A. The fires are due to dry, hot weather.
B. The fires are the deliberate actions of nongovernmental organizations whose funding has been cut?
C. The fires are due to the aggressive exploitation of the Brazilian rainforest.
D. The fires are an “internal issue” of Brazil and the countries directly involve.
It is considered that the Amazon forests produce about _______- of the world’s oxygen.
A. 10%
B. 20%
C. 12%
D. 15%
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