<span>In the context of English teaching methods in the US 'Previewing' is a term normally applied to a method that involves pre-reading new or unusual vocabulary before asking students to read a new text containing that vocabulary.
This technique is used to give the readers of the text an easier route into quicker comprehension of the piece.</span>
I can't understand your language
I think A is the best answer. You should go with A.
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<span>The Doppler effect is a shift frequency. If the frequency is lowered this is called a redshift (the opposite is called a blueshift). The redshift is said to support the expansion of the Universe , a tenant of the Big Bang theory.
Hope this helps
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