The scientist who discovered the two elements radium and polonium would be Marie Curie in 1898.
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The process of soil formation involves the following steps: Accumulation of materials, leaching and losses (because of weather factors particles are leached and eroded away or taken up from the soil by plants), Transformation and illluviation (the chemical weathering<span> of silt, sand, and the formation of clay minerals as well as the change of organic materials into decay resistant organic matter), p</span>odsolisation and translocations (strong acidic solutions breakdown the clay minerals). From the given options soil formation involves both <span>physical and chemical weathering of rocks. Correct answer:D</span>
That's "displacement". It only depends on the beginning and ending locations, and doesn't care about the route between them.
Answer:
D. crystalline solid that conducts current under certain conditions
Explanation:
Semiconductors are crystalline solids that has the ability to conduct electrical currents but on certain conditions e.g heat. The conduction of semiconductors is less than that of conductors (metals) but more than insulators (nonmetals), hence, they are said to be intermediates of conductors and insulators in terms of electrical conductivity.
Examples of semiconductors are silicon, boron, carbon, germanium, arsenic etc.
Answer:
The alternative energy sources are defined as those resources that are used in place of the natural and non-renewable resources. This resources plays an important role in the conservation of natural resources.
The fossil fuels are the resources on which the people are directly dependent. Burning up of these fossils leads to the emission of carbon, which has a direct impact on earth. A small increase in the amount of carbon dioxide can lead to the increase in the surface temperature of earth.
In addition to this, these fossil fuels such as coal, petroleum, oil and natural gases are found to be present in a limited proportion, and it is a very expensive process to obtain these resources, so sustainable development method must be adopted in order to save this natural resources for the future generation.
Some of the examples of alternative resources that are widely used in place of fossil fuels are wind energy, solar energy, tidal energy, biomass energy and bio-fuels.
Thus, it is very important to develop and use alternative resources.
