Almost（）substances expand in volume when heated and contract when cooled.
A. all
B. they all
C. all of
D. all are
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The word "obscure" in line 1 is closest in meaning to（）
A. interesting
B. unclear
C. imperfect
D. complex
The word "laborious" in line 8 is closest in meaning to（）
A. unfamiliar
B. primitive
C. skilled
D. difficult
下列各项中，（）适用于市场预测呈水平波动，无明显上升或下降趋势情况下的预测。
A. 高次指数平滑法
B. 趋势外推法
C. 一次指数平滑法
D. 弹性系数法
The author mentions twenty percent itl line 23 to indicate that（）
A. eagles are twenty percent bigger than most birds
B. twenty percent of all nests include foundation branches
C. the nests of eagles are twenty percent of larger than those of other birds
D. birds Can carry twenty percent of their own weight
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