举一反三
- Before ____________of synthetic dyes, yarns were often colored by dyes obtained from natural vegetable and mineral matter.
- What are the most important natural resources in Canada A: [A] Forest resources. B: [B] Mineral resources. C: [C] Water resources. D: [D] Agricultural resources.
- Organic chemicals mainly come from oil, natural gas, and . A: metal B: air C: water D: coal
- Electricity, gas and water were considered to be natural ______.
- Minerals,timber, land, and water are natural ______(s).
内容
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Before ____of<br/>synthetic dyes, yarns were often colored by dyes obtained from<br/>natural vegetable and mineral matter. A: introducing B: introduction C: the introduction D: introducing that
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Which of the following statements is false: ( ) A: Suspended solids are unstable and can be easily removed from the water. B: The colloidal particles are usually charged by adsorbing ions. C: The sizes of dissolved matters are less than 1 nm. D: The pollution of natural water only comes from the natural environment.
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of all organic chemical is obtained from crude oil and natural gas. A: 80% B: 99% C: 70% D: 79%
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As the natural process of creation of li...ource of all values.
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What happened after the researchers put painkilling medicine in the water? A: Fish that received the painful shot stayed in the natural section. B: Fish that received the painful shot moved into the empty section. C: All of the fish stayed in the natural section with plants and rocks. D: All of the fish moved into the empty section with painkilling medicine.