题目内容

In paragraph 5, the author describes an experiment in which water is poured into various glasses in order to

A. show how children approach difficult problems
B. recommend an experiment that can be done at home
C. give a variation on a classic experiment by Piaget
D. suggest an activity for parents and children

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Which sentence below best expresses the essential information in the highlighted sentence

A. The Norse were the first Europeans to discover North America, but little evidence remains of their settlement at Vinland.
B. The location of Vinland, the first European colony in North America, was unknown until the twenty—first century.
C. The Europeans chose Vinland as the site of their first colony because it had perfect conditions for growing grapes.
D. Eriksson's Vinland was the first European colony in North America, but scholars still disagree over exactly where it was.

Look at the four squares,A ,B ,C , and D, which indicate where the following sentence could be added to the passage.Where would the sentence best fit?
For example, they might estimate the number of black bears in a national park by counting individuals in a few sample plots representative of the whole park.
An important characteristic of any population is its density.A Population density is the number of individuals per unit, such as the number of maple trees per square kilometer in a county.B Ecologists can rarely determine population size by actually counting all individuals within geographical boundaries.C Instead, they often use a variety of sampling techniques to estimate densities and total population sizes.D In some cases, they estimate population size through indirect indicators, such as the number of nests or burrows, or signs such as tracks or droppings.

What can be inferred from paragraph 3 about annual crops and common property lands?

A. They have been part of agriculture for only the past fifty years.
B. They are not considered to be significant causes of soil degradation.
C. They produce more income than perennial crops and private lands do.
D. They may decrease soil fertility and agricultural productivity.

The word patches in paragraph 5 is closest in meaning to

A. dark places
B. family groups
C. warm spots
D. small areas

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