Which of the following statements can be inferred from paragraph 1 about the history of communication？
A. Certain advances in technology have greatly changed communication．
B. People have both loved and feared new developments in technology．
C. We do not know what people thought about before modern technology．
D. The history of modern communication began in the fifteenth century．
查看答案
The word each in paragraph 4 refers to
A. experiment
B. child
C. age
D. row
How are waterlogging and salinization related？
A. Salinization occurs only where waterlogging is a problem．
B. Waterlogging raises and concentrates salts near the surface．
C. Farmers add salts to irrigation water as a way to fertilize soil．
D. Both waterlogging and salinization contribute to soil erosion．
Why does the author mention corn and wheat yields in paragraph 7？
A. To illustrate the effect of a small amount of erosion
B. To explain why erosion affects only certain crops
C. To describe the result of a shift from traditional practices
D. To show how poor management influences crop yields
Why does the author mention words, gestures, and pictures in paragraph 2？
A. To list things that are used in experiments with children
B. To give examples of symbols that children can understand
C. To compare different ways of illustrating a child's experience
D. To illustrate the concept of conservation of quantity
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